FAQs about Fiddler
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Fiddler or Red Clawed Crabs; husbandry
To Whom It May Concern,
<Looks like me today!>
I have a 20 gallon glass aquarium. I live in an apartment and I'm allowed a 20
gallon vivarium/paludarium or a 10 gallon aquatic tank.
I'm interested in information about Fiddler or Red Clawed crabs.
<Interesting beasts. Red-Claws are probably easier to obtain, but Fiddlers are a
bit less likely to kill each other over time because they're so much easier to
sex. The males are very intolerant of one another, but a 'harem' of fiddlers
including a one or two males and 4-5 females would be perfectly doable in a tank
this size. Just make sure there's space enough for the males to avoid each
other. Plastic or wood bogwood roots to create a 3D maze of climbing places,
shored up with water worn pebbles and coral sand will work nicely. Both species
are tropical, so you will need to heat the system. A small aquarium heater in
the water could work, but be sure to get one the right size for the amount of
water in the tank; more than likely a 25W heater will be ample. I'd suggest
clipping an aquarium guard over the heater to prevent the crabs burning
themselves. A filter will be important too, but nothing too fancy. A simple
internal canister filter will be cheap, functional, and easy to clean. It will
need to go under the water completely though, perhaps lying on its side if the
water is just a few inches deep.>
All I know is that you need 1/2 play sand & 1/2 dechlorinated 1.010 salt water,
and rocks for them to climb.
<More or less. Basically, both species are hardy and adaptable. The precise
salinity isn't too important. Something like 10-15 grams per litre of tap water
will be fine (normal seawater being 35 grams per litre). Ideally, you'd use a
hydrometer to check the salinity (actually, the specific gravity) before use --
you can get cheap and cheerful plastic hydrometers on Amazon and the like for a
few dollars. While not particularly accurate, they're fine for brackish water
fishkeeping where ball-park numbers are adequate.>
I have tried to read the articles on brackish water, but I'm having a problem
understanding how to set up the tank, dietary needs, etc.
<Both these crabs are deposit feeders. In other words, they process mud and
sand, extracting algae and organic material. In the home you can feed them
virtually anything, from bits of seafood and cooked peas through to fish
flake and specialist crab food. I'd also ensure a good source of iodine, whether
in the form of seaweed (sushi nori for example) or else iodine drops sold for
marine aquaria, at one-half the recommended dose. Some specialist crustacean
foods include iodine -- check, and if yours does, it'll make a great staple.>
I would appreciate any assistance you could give me.
<Hope this helps, Neale.>
Two fiddler crabs flipped over 6/18/17
Hi, I am emailing you about our two fiddler crabs (with a big and small
<Likely two males>
We got them about 6 months ago from Wal-Mart, and I put them in my 10
gal freshwater tank. I did not realize how aggressive they were, and
after they ate 3 of my tetras, we put them in a 10 gal tank.
The tank had about 2 inches of water, half sand, and some rocks and
<There is space for them to get all the way out of the water I hope>
I fed the crabs fish food, some small bits of fruits and pieces of fish,
such as tuna or sockeye salmon. The crabs both molted several times and
got along for the most part.
This morning both of the crabs were flipped upside down! 1 seems dead
and 1 is still moving a bit, what happened?! what can I do?
<Do you have "water quality test kits?"; need to assess "if there's too
much of something/s and not enough of others". Fiddlers don't tolerate
nitrogenous waste accumulation, a lack of alkaline earths, low
alkalinity... I would change out all the water, rinse all materials in
the system, re-set up, add Dechloramination to remove sanitizer, and
treat w/ a commercial iodide/ate solution as gone over on WWM>
I just read about the crabs needing salt, so I put a tiny bit of
aquarium salt by them.
Is there anything I can do?
<See above and WWM (the search tool on every page or all linked to the
<Do write back if all is not clear once you've read/studied. Bob Fenner>
Re: two fiddler crabs flipped over 6/19/17
Thank you for your speedy response!
Yes, the tank is half a sand beach, and they can climb the rocks to get
out of the water too.
We got them after feeling sorry for them at Wal-Mart, but have become
quite attached, especially for their "waving" antics. I did not know
anything about crabs really.
<Males "wave" to attract females mostly; and to ward off, threaten
Shortly after adding the salt, they both perked up, flipped over, and
started traveling around.
<Ahh! Great news. Could be a few possibilities here... something as
simple as Nitrite poisoning... again, I would invest in simple test
kits... And adhere to a maintenance schedule; washing, flushing out the
It was amazing. Most of the posts on your site has things about crabs
<Mmm; a bunch to state here; but no doubt orders of magnitude more
organisms are killed by mis-use of salts (combinations of metals and
non-metals) than aided. How much salt is in your source water? Many
organisms need "some", but very few are aided by more being added
Again, my urging you/all to get use testing gear. A simple hydrometer is
of use for specific gravity, indirectly salinity... OR after cleaning,
adding about the same amount of sea salt (NOT table/NaCl) to about the
volume of water each cleaning>
Thanks a bunch!
<Certainly welcome. Bob Fenner>
re: two fiddler crabs flipped over..
Oh I cleaned their tank etc as well.
Been awhile (not Fiddler Crab Related per se)
Saw you and your wife just had a baby girl - Congrats :)
I know you live "overseas" ~ just curious if you were close to Southampton at
all....my brother took a job as a percussionist on Cunard's Queen Mary 2 and
their major ports are New York and Southampton, so he is there quite often. He
has also been to Oslo, Hamburg, Le Havre, Bruges, and a bunch of other places
all over Europe.
<Where I live is nowhere near Southampton! But sounds like your brother has a
Regarding my Fiddler experiences, well, I've gone through ups and downs.
I've lost a few over time. I have come to realize it isn't anything I am doing
incorrectly. Some it seems it was most likely their time as they were over a
year old. One seemed to pass away because she couldn't molt, just as one boy
passed right after he molted. Some seemed fine and then passed away seemingly
out of nowhere. Some of them passed in pairs (a male would pass and then the
next day a female passed in the exact same spot as he had - and they had been a
<Indeed. Fiddlers probably aren't all that long lived to begin with, a couple
years probably, and the ones seen in pet stores are presumably around a year old
when they get them, since the larvae take the best part of a year to complete
their maturation process into actual crabs. So yes, once you buy them, you're
probably going to keep them for 1-2 years, tops.
A few months is not right, so you'd review maintenance if that was the case, but
above a year, you're probably doing the right things, though as always, reading
about the animals and tweaking their habitat is always worthwhile.>
Right now I have six, two boys and four girls. One of my girls I got from Petco,
not realizing she only had two legs on one side and one leg on the other.....I
was VERY worried about her when I got her home but decided I would keep her
because she would die if I took her back. In the tank one of my more shy females
took a liking to her and allowed her to hide in her special spot. I must say she
was a feisty little thing, even with her three legs she was not going to take
anything from anyone!!!! Within two days of me getting her - she molted and got
all of her legs back, except for one!!! She has kept up her feisty spirit
I also have one female which is very unique. She is the more shy female who had
taken the one under her wing. This particular female is VERY human friendly. She
loves to sit up on the ledge and wait for me to get her. I will pick her up and
she loves to crawl all over me...especially under my sweatshirt arm, where she
will sit and hide. She also loves to have free time where I put her in the
bathroom and close off all "dangers" and let her run around - sometimes I will
put a towel down in the bathtub so she is safe and let her crawl around in there
for awhile. When it is time for her to go back in the tank, she is not too happy
and will try to crawl up my arm to avoid going back in. I feel bad for her.
Overall she gets along with the other crabs but she just enjoys coming out of
I have another cute female who will sit by the glass close to me and if I put my
finger close to her, she will put her little claws up in "fighting mode". It is
I've had a few pregnant females but for the most part, not too many. I had one
male who was relatively aggressive but he passed away (the one who tried to molt
or was ready to and didn't....). Since then I have one larger male and one
smaller male and they are not too aggressive overall.
The tank is still a pain to clean since they love their sand. But with the
Plexi-glass thing I devised, it is much easier to clean.
Well, it is Thanksgiving here....not sure about there......lol.....
<Not so much, no. But retailers are trying to invent Black Friday here.>
Either way, happy holidays!!
<And you, Neale.>
Uca; trouble 9/18/15
My friend gave me fiddler crabs, said they were easy.
A week later they died. That’s when I actually looked up how to care for them.
Spent a lot of money on different habitat space, (takes a lot of rocks to have a
filter and land). Bought two red claws, week later they died. Did more
reading/research added a sand substrate, made sure environment was consistant
for a couple of weeks, then added 2 more red claws. they were fighting on the
<Need to be transported separately>
Anyway the one was dead after 3 days with both claws missing. I thought the
other dead because it hadn’t changed location for a very long time. T
<How large a system? Both males?>
old my husband to dispose of it but he asked what was I talking about it was
moving. It stays in same land cave all day barley moving. I assume it’s
preparing to molt. Every morning I’m sure its dead and then it gives another
slight movement and is occasionally bubbling at the mouth(for breathing I’ve
However, today It is upside down, but is still slightly moving. I’m leaving it
alone because I read to not bother it during molt. There is little information
anywhere on the molting process or behavior. Is this crab going to make it or is
it like a bad movie with a long drawn out death scene?
<Much more likely the latter>
What can I do, if anything to help? It’s been 3 days of this behavior is it
going to make it?
Any help would be wonderful. These pets are cool but have had me worried and
stressed out for weeks! I told my son this was the last try then he can have a
<Have you read here:
Do so. Bob Fenner>
Re: my crabbies..... Uca, and shared feline insights...
Well, no news on the crab end is good news right?
<So they tell me...>
I think you have a bit to learn about these little creatures. I
know you are the expert and have told me they don't mourn and they
aren't all that social.
<That is my/most people's experience of these animals. Indeed, many
species are downright aggressive towards one another. But I'm sure there
However, I swear the larger female left from my other group of four
mourned the loss of her other female mate, as she did not want anything
to do with the two new babies. And the two new babies paired up and were
stuck like glue to one another - that is until.......the new little
female molted. At that point, she wanted to be left alone for a
bit. She lost a leg in the molt and didn't want anything to do
with the male. She just wanted to hide out under one of the
What happened next was quite interesting....the male seemed frustrated,
so what he did was he decided he was going to play with the larger
Now, Ms. Stepsister/Mistress got quite annoyed by the Little Prince...to
begin with. He started by following her around the tank little a
little puppy. She kept going away from him.
<Quite so, but in biological terms "no" doesn't always mean "no". Many
female animals deliberately test the persistence of the male as a way of
gauging genetic fitness. Squirrels for example do this a lot, and in
their mating season you'll see them chasing one another up and down
trees. If the male can keep up, the female is more likely to judge him
an acceptable mate. Since females get few chances to mate and breed
successfully, they place a high premium on genetically fit males, so
tend to be picky. Males, being able to crank out as much sperm as they
want, and in the vast majority of cases not having to do anything
towards rearing the young, aren't picky, since the best thing for them
is to mate as often as possible, and so spread their genes out as widely
as they can. In other words, females and males have different agendas
when it comes to mating... no real surprises there then!>
Finally at some point, she started to let him get closer. He got
close enough to touch her with his claws and then she would run away.
He would then follow her, touch her with his claws, and she would run
away. This happened for awhile. Finally, he decided to stop
and went away. She must have decided she missed having someone
around or that she didn't mind him after all, because she went and found
him and touched him with her claws and ran away. He realized she did
this and so she went back after her and they started this game of "touch
the claw" almost like "tag" with back and forth - she would come find
him and touch his claws and play with him and then run and he would go
find her climb on top of her or touch her claws, and run off. This
went on for hours!!!!
<Could be socialising, but the question is why. In some animal species,
particularly those where males and females are rivals or even physical
threats to each other, there needs to be a "secret code" as Leonard
Cohen might sing, that pleases both partners. The classic examples are
among spiders, where females are bigger than males and liable to treat
them as food. So the male has to do something to persuade her that he
isn't a fly stepping into her web (despite having 8 eyes most
non-jumping spiders have poor vision). So he taps her web in a very
specific way, a kind of cross between a flirty dance and Morse code, the
result of which -- if he does it properly -- switches off (usually) her
potentially predatory instincts. If he gets it wrong and she eats him,
then that was proof positive he had poor genes, so no harm done! Good
genes means a good ability to remember and perform the secret code.
Among your crabs you could be seeing something similar. Since hardly
anyone studies crustaceans compared to insects, our knowledge of their
behaviour is surprisingly limited, but there is some understanding that
Fiddler Crabs are capable communicators, at least so far as "claw
waving" goes. You may be observing, and reporting, something that hasn't
been studied before. Certainly not to my knowledge, anyway (which isn't
Each would lie in wait after they ran away to see if the other would
come and if the other didn't come fast enough, the other would go back
after the other one again to remind the one they were still playing.
It was hilarious. Ever since that day now, whenever the Little
Prince does his waving stuff, she will come by him. I think the
little female get a bit jealous sometimes because she will come in and
resume her place as if to say....."wait a minute....he's mine
honey....." So, the good thing out of it is the older female has
come out of mourning and is back to going around the tank rather than
hiding all the time. The three of them overall seem to be doing
well, with the exception of some slight jealously between the little
female and the older female......but is only slight jealously when the
older female pays attention to the male.
<All sounds very interesting, and as you suggest, may have some social
implication that isn't obvious to us. Regular readers of my replies will
know that I don't ever say that animals lack feelings or social
interactions, but rather than it's risky to assume they are the same as
ours, though in some cases they may be.>
In some other bad news, both my Pittie and my oldest cat Kissy (a Sphynx
hairless) have mast cell cancer tumors. So that has been
stressful for our home. Monetarily it was bad when I found out my
Pittie had it...but then I found out my cat had it just today.
Additionally we had been waiting on some results to find out if my mom
had cancer but luckily her results were negative!!!!
<Ah, that is good news. Shame about your cats though.>
Anyway, I wanted to let you know how things were in our crabby world and
how things were going. I know some of it goes against what you
tell me about them but their actions are just strange and how they
seemed to enjoy playing with one another. I enjoyed watching them,
that's for sure. They were just too darn cute they way they ran
back and forth. It really looked like a game of "tag.....you're
it....no....tag...you're it......" haha.
Hope you are doing well.
<Thanks for the update, and good luck with all that's going on. Cheers,
Mr. Crabby....... horniness... repro. f' (Fiddler)
I had a new question for you....and I am sure this one is going to sound
a bit goofy because again, I am going to be attributing traits to the
crabs which they probably don't have....but this is just odd and you
know the history of Mr. Crabby and his, well, ummmm, horniness....for
lack of a better term, so here it goes....
Recently after the girls molted, I realized the crab who passed away was
not the one I thought, but was actually Mrs. Crabby....the "mate" who
was purchased for Mr. Crabby and had been with him since the beginning -
AND - the one he liked to mate with (literally) the most. As you
know, he nearly had her constantly with eggs. When we got the
mistresses, he would also mate with both of them - the larger female
more often than the smaller female, but he would mate with both of them
as many times I had all three females carrying eggs. However,
since the passing, of what I know now to be Mrs. Crabby, Mr. Crabby has
not mated with either of the mistresses!!!!!
I have not had any females with eggs at all!!!! What is up with
<No real idea. But could be seasonal, dietary, age-related...>
Did he lose his "mojo"? I mean, he still does his little crabby
to show off. He actually does it a lot.
<Quite so, but some of this display is aimed at other males and as much
about asserting status and territorial boundaries as attracting
Is it the girls who are somehow not allowing him to mate with them?
It seems like they really didn't have a choice in the matter before.
<There may well be elements of this, yes, females choosing whether or
not to mate.>
I really just don't get it!!!! Not that I am complaining mind
you.....I just find it odd. You know one of my main things was
having the girls with eggs, eggs, eggs, and more eggs. And
now....NOTHING. It is so strange.
Any ideas on why?
<There's a vast literature on mate selection out there, and you may find
some of the primers, like the excellent "King Solomon's Ring" worth a
Lorenz was interested in vertebrates, especially fish, birds and
mammals, but the basic ideas seem to be applicable across the animal
My assumption of course would be the human trait of him missing his mate
and now that she is gone he won't mate with the others but it was okay
when she was around. But I know you are going to tell me that is a
human thing and the crabs aren't like that....so then what is it???
<It's complicated, just as with humans. For sure crabs don't have human
motivations, but that isn't to say that both crabs and humans can be
motivated by similar drives and desires that are deeply rooted in a
shared evolutionary history.>
Anyway....in other news, I've had quite a few successful moltings in the
past few months - at least one or two from the male, a few from each
female - basically they are all the same size right now. It was
interesting as after I did a tank cleaning, added my calcium, iodide,
and fed them, two molted; then this past week, I had added a bit of
water, fed them, added the calcium and iodide, my mom and I ran some
errands and when we got home, one of the females molted. Normally
they tend to molt overnight, but I added all this just before we left
and we came home to a fresh molt. It definitely seems to help with
the added supplements to the water.
<Yes indeed, the addition of iodine seems to be a huge tonic to crabs
and crayfish generally; it's a shame this inexpensive addition isn't
more widely recognised and purchased.>
And those crabbies all love when I do a tank cleaning - they go nuts
eating sand when they get back into their tank!!!! Seriously, I
can't even see those girls claws move because they go so fast. I
love watching them. It is funny to watch Mr. Crabby with the one
claw shoving the sand in. I think they are also happy with the
Plexi-glass set-up with more water.
<This does seem true about crabs, even amphibious ones, in captivity;
while they certainly do need land above the waterline, they're less
scared of going underwater in aquaria than they are in the wild,
presumably because they see there are no predators there.>
They all have areas to get away from one another if they want and have
more hiding spaces than just the one spot - it has also helped for
molting because they all used to go into the chest to molt and now they
have molted all over the tank in the various "ornaments" I have for
Well, anyway, let me know your thoughts on Mr. Crabby's seemingly change
Perhaps a bit of this? RMF
Re: Mr. Crabby....... repro., stkg.
Thanks for your input....now here's another question for you.....
Are the three of them okay the way they are and should I leave things
alone? OR - should I add another female (or two)? Would that "rock
the boat" too much, so to speak? I assume adding one more female
(most likely of a smaller size) wouldn't be the best idea since all
three are of the same size, so I would probably have to add two.
Would this put a spark under Mr. Crabby again? AND - do I really
<If they're happy enough now, I'd leave them be; but as/when you need to
add more, yes, adding more than one will minimise any risk of trouble.>
Since I have no other males in the tank, I assume he does his Crabby man
dance for the girls. (Or does he have to move that big claw around
for "exercise" to keep it mobile?) If he does it for the gals,
then I assume he still is trying to impress the girls, but they are
<It's hard to explain all the motivations behind a certain behaviour,
and just like many of our behaviours, there may be multiple reasons;
e.g., we may smile when happy, but also when trying to appease someone,
or when nervous and trying to convey otherwise... In short, few animal
behaviours literally mean just a single thing.>
**One off-topic thing is I know you say iodine is good for these
guys...and a friend of mine recently got hermit crabs....is iodine good
for them as well and if so, how do you give it to them?
<Yes, is almost certainly good for them too.>
I have been sharing some info I know about hermit crabs, which they
didn't know - such as the salt water and the fresh water bowls, the kind
of shells for them, etc. - they were clueless as the first hermie they
got was "won" at a carnival for their little girl (and it didn't make it
through the night) - just horrible to hear these kinds of things!!!!!
But, it got
their little girl wanting another one, so they got two more at a pet
store the next day and the pet store sent them home with all the wrong
stuff. Once I talked to them, they realized that, and the
following day realized they needed to go back and get all sorts of new
stuff and wound up spending over $100+.....all because of a carnival
<Ah, we have the same problem here with Goldfish given away at fun fairs
(US: "carnivals") as prizes. The fish itself may effectively be free,
but the ethical owner finds themselves with substantial expense if they
don't already have a pond or aquarium at home. There's some moves to ban
giving away live animals as prizes, and to be fair, it's dying out
anyway, as many fairs seem to prefer giving away soft toys and other
cheap tat instead of Goldfish.>
But at least it seems they got a somewhat good handle on things. I
just wanted to know - other than humidity, temperature, the salt
water/freshwater, climbing ornaments, multiple good shells, etc. what
else I could tell them. As I said, I know the calcium and iodine
are good for the Fiddlers, but does it help hermit crabs too? What
other good info, if any, do you have?
<You can certainly start reading up on marine Hermits, which apart from
being underwater animals, have identical care:
But you can also peruse the MANY questions we've had on these beasties
over the years, here:
Follow the links for more. Unfortunately, we haven't yet written an
article on their care. Something I may well do now!>
I know it is off base from the Fiddlers, but I figured I would ask
quickly so they at least have a basic start. If you don't know
much about them, that's fine too - I am not getting into hermit crabs
any time soon myself :) I think they are cute and like them quite
a bit, but the Fiddlers are such a learning curve for me and I don't
think people realize how these little creatures have so much knowledge
needed to adequately take care of them and give them a good life!!!!
Especially when mall kiosks and carnivals have hermit crabs with all
those fake painted shells - so not nice!!!!
I meant to ask if you if you have a Facebook page of anything of that
I know at one point you mentioned attributing human traits to animals
and you said you had a catfish named Claire, who you talk to and
introduce to houseguests. You also said it wasn't a bad thing to
"make a Facebook page for your dog." I don't believe I emailed
after that, probably because I didn't want to say that, in fact, I do
have a Facebook page for, not only
my dog, but each of my two cats, as well as myself. My one cat's
page is the one used most often - because she is my most "vocal"
https://www.facebook.com/Chloe.Woey. She is even "married" and Mr.
Crabby officiated the ceremony - attached is the photo :) "She"
also posts photos of the crabbies and our other animals (we have a total
of three dogs and three cats in our house!! - my mom is owned by one cat
and two dogs....I am owned by two cats and one dog....and of course the
<I do have a Facebook, and occasionally put pet-related posts up, but to
be honest I don't use Facebook that much -- mostly to share photos with
Anyway, again, your advice is always appreciated. Somehow I think
I will always have questions about these little Fiddler critters......so
I highly doubt you'll stop hearing from me anytime soon, so I hope you
<Not a problem.>
Oh - and I know you talked about that article in Coral Magazine and I
had found Part 1, but you had said that Part 2 should be in the next
issue and when I looked, I didn't see the second part in the upcoming
issue. Could you tell me if you found Part 2?
<I have not yet received/read the next issue of this magazine, but I did
ask the publisher not to send them to me any more because I don't keep
marines and didn't want him to waste his money on this kindness. He is
sending me their excellent freshwater magazine though, Amazonas. Anyway,
you may want to visit their website, here:
I'm sure you can find back issues, contact details etc. there.>
<Most welcome, Neale.>
Mr. Crabby.......not such good news; repro. f'; Mortuus est
Some bad news.....Mr. Crabby is no longer with us. He must have
passed away sometime this past evening and I noticed a little while ago
when I checked in on them that he was sitting in the middle of the water
and it looked like he was not "standing" on some of his legs.
I am not sure what happened. I can tell you a few things and
perhaps you will say maybe it was this or that or none of the above.
One was that recently he was trying to mate endlessly with the two girls
and they were running away from him like crazy - trying to get away from
him....as in trying to climb the filter cords, scurrying all over trying
to hide, etc.
Finally I went into the aquarium and made it easier for them to hide
from him and gave them some food and watched them for a while as it
seemed to get somewhat vicious a few times when he did manage to catch
them and they got away from them. He gave up after a while and
seemed to not be interested again since that day, which was about a week
or so ago. Could me preventing him from mating or trying to
prevent it (since he hadn't shown interest in forever and then he had
and I stopped it) be a reason he died?
<Unlikely; indeed, exhaustion from mating more often in captivity than
in the wild (where animals have to spend more time finding food and
escaping from threats) can cause animals to have shorter lives in
captivity. To be fair, this applies most obviously to females which put
more energy into reproduction. But it might be a factor with males,
The next thing that happened was the top glass part of the tank wound up
breaking on me, by accident of course and in the meanwhile, I have used
a piece of Plexiglas as a cover. The main difference between the
glass and the cover is the glass had a U-shape in it for the screen
cover for air to get in better, whereas the Plexiglas does not.
Could the lack of that small bit of oxygen through the screen be a
reason for his death somehow?
<Again unlikely, but it is worth checking that you have at least a
couple of openings to air can move through the tank. Fungi can develop
in tanks where the air is too still, and that in turn can cause
problems. Do look at modern frog vivaria, as these are very well
designed. You can find DIY designs online if your local retailer doesn't
have them. You needn't buy one, but do look at how they are put
together, and use that as inspiration.>
The girls are both okay, as far as I know. The only other thing I
could think of is possibly a small piece of glass could have gotten into
the tank? But the glass top broke nearly a week ago as well, so I
am not sure if that could be it. I guess I am trying to suggest
all options to see if any are possibilities and what you suggest might
may be the most likely for his death.
<Most animals are smart enough to avoid chunks of glass, and given they
have exoskeletons not soft skin, it doesn't seem likely your crabs could
Third, I told you he hadn't been acting the same since the death of Mrs.
Crabby, and that was less than three months ago.....could that have
anything to do with his passing finally?
<Possibly, but only in the sense that these animals likely have
relatively short life spans, probably a couple years, >
I clean the tank regularly, but I guess there is always a possibility
that something in the tank could have killed him? Or perhaps could
a large piece of food done it? I had just fed krill a day or so
before. Could it have been a bad piece of krill?
<Again, it's possible, but these animals are carrion feeders, so they
should be pre-adapted to eating dead material.>
From all the looks of it, Mr. Crabby didn't look sick - he had all his
limbs, his eyes were upright, his color looked good. He was
probably about a year old or so - not really sure - I got him in about
October or so of 2012. Could it just have been "his time"?
Since he was bought from Wal-mart and therefore not given a good start
off right from the beginning?
<Possibly; if you've had him a year, and maybe he was at Wal-Mart for a
few months, and would have been a few months old (at least) at the time
of capture, you can imagine he might have reached a ripe old age in your
care and died a natural death.>
My next question is - now I have two females...the two which were bought
together. Do I just leave them be as a pair, if not, what do I add
to the tank? I am going to wait until I get the new top for the
tank replaced, which is going to cost me $60!!! I am
also going to do a good scrub down of the tank tomorrow (since it is
3:30am here now) since he passed away in the water. Once that is
done, it is kind of a large tank for just the two gals isn't it?
Will they miss a boy or not? Do males just cause trouble...hehehe?
<The females are fine together. You could add some more, but I'd keep
outnumbering males with females (1 m: 3 f, 2 m: 5 f, something like
You could also try combining with other livestock from the same
environment depending on the size of your aquarium. There are some small
marine Hermit Crabs for example that could cohabit, and Fiddlers will be
just as happy with marine water as brackish. There are some brackish
water hermits about too, often sold in shopping malls as novelty pets.
In sufficiently large tanks, you could combine Fiddlers with small
brackish water fish like Mollies or "feeder" Guppies, but even for
Guppies you'd want 10+ gallons of water.>
Anyway, I will say I am going to miss my Mr. Crabby little man
dance.....definitely a sad evening over here. At least now he can
go be with his Mrs. Crabby over that big Rainbow Bridge :)
Hope all is well with you,
<Actually, been a difficult couple days, but glad to be here at WWM
helping out. Cheers, Neale.>
Re: Mr. Crabby.......not such good news
I decided because the two females were rather, well, boring (the tank
always looked empty cause they were always hiding)....and the male is
the one who is....well, interesting to watch (is that bad to say?)....so
I got a little male and female pair. When I say little, I mean
little. At first when I took pictures, people didn't see a
difference until I took the picture I've attached to show the size
difference. Obviously the little female is on the far left, the
male is in the middle and the older female is on the far right.
The "mistresses" have a new name because of how they reacted to the new
little ones - well, actually only one acted a certain way, but they both
get the nickname :) which is the "evil
<Oh dear. Do bear in mind that crabs are notoriously unsentimental when
it comes to social relations. In other words, they view weaker specimens
of their kind as, at best, competitors to be driven away, and at worse
as meals! That said, your photos don't suggest they're terribly
different in size, so with luck all will be well.>
At first when I got them I took the two older girls out, put the new
little ones in, fed them, and they were hungry as ever. I don't
believe I have ever seen the crabs eat every morsel of food I gave!!!!!!
Of course they poo'ed a lot too. Once they ate a bit I added my
other girls back in - after I also had added more food as well.
The one girl just went toward the back and didn't give the new ones any
mind, but the other female insisted on trying to pick fights and chase
after the little ones. So I was on crabbie watch for a while.
Finally the older one gave up and I think it gave the little ones some
courage too....haha. The next time the bigger one came around, the
little male put his little claw up (which is about as big as the older
girls small claws.....lol) and acted all tough.
It was quite humorous. The little female also wasn't taking any
"you know what" either. AND within probably an hour or so, the little
Prince (well, if there are evil stepsisters.....there has to be a Prince
right?) was trying to attempt the crabbie dance. He wasn't very
coordinated yet with it, but he was trying. And he was trying when
the girls came into sight even more. It was SO cute.
<I bet. While these behaviours are surely inbuilt instincts, there's a
certain amount of trial and error involved before the males get their
particular "routine" figured out. Watching animals polish these
instincts can be fun to watch from out (supposedly) rational and more
advanced perspective. But I bet my cat finds watching me clumsily bump
into tables and knock stuff off shelves absolutely hilarious.>
I am debating getting a larger tank; however, that means more cleaning
and I am such a neat freak and a larger tank means more difficult to
clean - and more sand and more stuff to clean and all that jazz.
So, we'll see.
<With Fiddlers, there isn't a pressing need for a huge tank, especially
if you can add three-dimensional stuff like plastic roots and fake
plants for them to clamber around.>
Okay, so now I am done with my boring story.....haha. I do have
one question which I may have asked before.....as you can see in the
picture - the two new crabbies are much brighter in color than my older
Usually they are that bright orangish color when I get them and change
to the duller brownish color within a week or so. Does this have
to do with them being kept completely underwater freshwater and then I
put them into the brackish salt with access to land? Is it due to
lack of diet at the store?
<Could easily be, so some combination, or else differences in collection
site or even species.>
I don't think they feed them all that much or at all - I know because
whenever I buy them they come home and eat and eat and eat. Is it
due to lack of moltings?
<I do imagine many pet stores don't know *what* to feed Fiddlers, so
leave them to eat whatever scrap fish food they have lying around.>
Is it due to immaturity? I know the older gals have "hair on their
legs" and the younger ones don't...so it is age-related somehow? I
guess I am clueless as the change in color but it always happens.
<Indeed. Colour changes in crabs as they age is very common. But as they
age they moult less often, with the result that their shells often
become darker, sometimes more grubby-looking, and often encrusted with
algae, barnacles, sponges and so on (which probably help as
Sorry to hear you've had some difficult days - I hope nothing too major.
<Somewhat major for my wife and I; not the best week we've shared.>
Anything I can help with? You've helped me a lot, so if there is
anything, let me know. I am a good listener and great advice giver
- I just don't know much about these little crabbie creatures. My
degrees (a Bachelor's and a Master's) are in Psychology, plus an MBA,
and I went to medical school (but alas did not finish due to some
extenuating circumstances) and I have recently started Life Coaching
business :) My business came out of a lot of education and
difficult years for me.
<Ah, mindful of Khalil Gibran's comment that work should be love given
<You too, Neale.>
RE: another sad story... Fiddlers
Well, it seems the addition of the two little ones disturbed the
Mistresses of the tank a bit much. I knew one (the larger one I
purchased initially) was ready to molt and she seemed to be trying to
find places to go but the little ones were bugging her. However,
after the first day or so they all seemed to be getting along so I
figured she would be fine. Well, needless to say, I decided to
clean the tank a few days ago, and as I picked up the tank, I saw a leg
and then she floated out from under the heater. As far as we know
she was alive until just a few hours prior so we are not sure what
happened exactly. Could it have been from not molting that caused
her death? I know when I took out the leg which had fallen off,
the outer shell crumbled in my hand and there was a leg in it - but it
<Yes, moulting is often the "weak link" in the chain when it comes to
keep crabs and shrimps. The use of marine aquarium iodine supplement is
a tremendous help. Failing that, iodine-rich foods should be used,
particularly seaweed (e.g., Nori). Do have a read here:
While that article is about crayfish, the basics hold true across the
board when it comes to large crustaceans.>
So, now I think the other older gal is ready to molt as she isn't
looking so great. The tank also has an odd odor and I just cleaned
it a few days ago. I am not sure what to do - if I should leave her
alone and hope she molts or if I should do something to change things
<I would change at least 50% of the water, perhaps all of it. Since
these are terrestrial crabs to some degree, you can remove them to a
bowl or bucket, add enough water to keep them wet (about halfway up
their legs should do) and put a towel over to keep them dark and humid.
Clean the tank, change the water, then put the crabs back. Changes in
salinity won't be a problem for them -- in the wild they'd experience
dramatic water chemistry changes. If at all practical, up the salinity a
bit, to around half-strength seawater if it isn't already there; that
would be about 15 grams marine aquarium salt per litre, or around SG
I didn't figure buying the new little ones would cause the one to die on
me!!! That was the last thing I wanted!!!!! I feel just
I am not sure what to do now.
<Hope this helps. Cheers, Neale.>
|RE: another sad story
I do use iodine supplement in the water - and I use it especially more
often if I believe it is time to molt. The girl seemed to want to
attached is a picture of her belly separating. She was in the "chest"
ornament for a few days prior to the new little ones which usually means it
is time to molt. However, when we got the new little ones, every time
went into the chest after we got the little ones, they bothered her and she
would leave the chest....or run from them. Basically they wouldn't
her alone the first few nights. When she did get a moment to herself,
started to eat off some parts of her "mandible area". I figured after
first day or two when they all seemed to be getting along, she would go and
molt but she never did and then she passed away.
<Unfortunate. The real problem here is that few people keep Fiddlers for
anything other than "temporary" pets, and our understanding of their needs
isn't very deep. Broadly, they seem to need what Mudskippers need: warmth,
humidity, a mix of dry land and brackish water, and a varied diet. But
beyond that, specific problems (let alone treatments) aren't much
understood. Do read some of BobF's work on marine/reef crabs, as these will
likely be informative. Rest assured that in marine tanks most crabs have
proven to be very hardy, virtually maintenance-free pets, and it's likely
if you do figure things out with your Fiddlers, they'll likely be good pets
too. It may well be that if the crabs have been kept in the wrong
conditions for too long by the retailer, they never properly recover. So
getting "fresh" specimens and quickly adapting them to your proper/better
conditions will work out the best.>
After she passed, I did a very thorough cleaning of the entire tank -
scrubbed all the ornaments, etc. I always take the crabs out and have
small habitats for them somewhat as you suggested - small plastic
containers, some sand substrate on the bottom, some gravel just out of the
water level, water about 1/2"-3/4" (same salinity as the water in the tank
- warmed), an ornament for them to hide in or walk around in), and
covered...although I usually cover with plastic wrap (with air holes poked
Since the water is smelling again, even though I did the tank cleaning this
past Saturday I will do a slight water change as you suggested and change
the salinity a bit. I hope that helps.
<If the water smells, likely filtration isn't adequate and the aquarium
needs a better cleaning protocol. I'd be using a robust filter (perhaps an
internal canister laid on its side) that gives a really good strong
current. Do remember these animals scuttle in and out of the waves, so
water current isn't something they dislike.>
As always - thanks for your advice. Hopefully next time it will be
<Good luck, Neale.>
My fiddler crab Crunchy needs help 9/12/13
Something is wrong with his shell on his mouth it almost looks
broken he keeps pulling at it and I'm really becoming
concerned. I can see the "mouth wipers" on the inside moving and it just
looks all together swollen and poofy. There are only guppies and ghost
shrimp in the tank with him. He hasn't been doing his mating dance he
used to do pretty regularly and the
two females I had recently died one was trying to molt but wasn't able
to the other I'm not certain. Please help I'm so worried about Crunchy.
<Do start READING here:
Basically, the three keys to success are brackish water (not freshwater
or water with aquarium/tonic salt); a diet with adequate calcium
carbonate (e.g., krill or unshelled shrimp); and last but definitely NOT
least, the addition of Iodine to the aquarium water (from marine
aquarium shops, very inexpensive, and even better, use at one-half the
dose stated on the
bottle). Get all these three things right and Fiddlers are super-easy to
keep. Ignore them, and as you've seen, moults fail sooner or later. Hope
this helps, Neale.>
Fiddler Crab questions - behaviors, molting, etc.
I purchased one male fiddler crab from Wal-Mart (kept in a Betta
container) about a month and a half ago. Due to various
information, I finally got him settled in a six gallon tank with half
sand sloped down to water with a 50w heater in the water and a small
submersible filter. The heater keeps the water at about 78-80 and
the tank is the Fluval tank and keep in humidity well. I have a
variety of hiding places (a small treasure chest, a bridge, a climbing
turtle) which are in the water but stick out of the water as well.
On the sand, I have a large log-like structure for hiding or crawling
on/through. I fed him shrimp pellets and he seemed to like eating
the sand as well as the pellets. Everything went well for the
first two weeks but then he seemed to get bored. I had been
looking for a female for him and found one at Petco. She was kept
fully underwater in a freshwater tank. Since I had been checking
frequently, I believe I got her within a day or so of them getting her.
Upon bringing her home and introducing her to my male, his initial
reaction was to stop and stare at her but then he started to show off
for her and has seemed happier ever since.
<Sounds great fun!>
My first question is in regard to getting them switched from freshwater
to saltwater/brackish water. I have been using distilled water
right now and they are doing well. I know I am supposed to use
some form of saltwater, but have no clue how to switch them over.
<Not a problem.>
I have been told not to just add salt as they could die due to the way
they breathe in freshwater vs. saltwater. Someone told me to make
sure to do the switch very slowly but I am not sure how slowly to do
<Changing slowly would be nice, but isn't critical. Fiddler Crabs (Uca
spp.) can switch between salinities very easily. Basically, do your
regular water change this weekend, but replace the water you take out
with brackish water around SG 1.005 (that's about 9 grammes of marine
aquarium salt dissolved in each litre of water).>
Second, I have had the male for a month and a half, the female for about
a month. Neither have molted. Is this normal?
<They will moult as/when they need to; don't worry too much. Lack of
iodine is an issue, but iodine-rich foods (like Sushi Nori) or
crab-specific, iodine-enriched foods should prevent any problems.>
Third, my male has been putting one eye down when he comes out of the
water the past few days. He does put it up when he is in the
water, but not completely straight up. Does he have a problem with
his eye that I can do something about or is this a sign of something
<Hard to say. But wouldn't worry overly much if he is otherwise active
and healthy. Fixing the salinity will be a terrific boost to their
health as well.>
Fourth, I have tried to feed them other food - Hikari crab cuisine, crab
pellets, etc. with extra calcium, but they seem to only like the shrimp
pellets. Should I try other things or is feeding just the shrimp
<They are scavengers, and in captivity a good diet places the accent on
algae (i.e., seaweed/Sushi Nori) and whole seafood (e.g., krill or
Fifth, even with the sand substrate they do not dig or tunnel, as I have
read some like to do..is it normal for them not to do so or do I have
the sand packed too tight?
<Could be. Don't worry too much for now. Provided they have somewhere
damp they can rest, they don't really need a burrow as such.>
Sixth, do they like change, i.e. changing up the decorations in their
habitat, or do they not care, or do they like things the same?
<Most animals prefer things left alone, but tidying up the tank every
few weeks, cleaning behind rocks and suchlike, and then rearranging the
tank a bit will be beneficial, providing some stimulation they might
Finally, even with the filter, the water seems to get cloudy within a
day or so. Is this normal?
I feel like I should be changing the water all the time to keep the
water clear - as the female seems to not like to go in the water as much
when the water is dirty.
<Indeed, this is likely so. But do also recall that Fiddlers barely
enter the water in the wild, only doing so to "freshen up" their gills
as they dry out, and in the case of females, to release their eggs. More
than 90% of the time they are on land.>
Additionally, there seems to be more smell, despite me trying to keep
things clean. Any advice?
<Feed less, don't clutter the tank, clean behind ornaments more often,
and use a turkey baster to remove uneaten food after a few minutes.
Stronger filtration can always help. Let the crabs eat more algae (Sushi
Nori) rather than meaty foods like pellets. Don't worry about starving
Sorry for the length of the email, but there is just so little
information out there, let alone good and valid information!!!
<Hmm… do read:
Crabs are, for the most part, extremely hardy animals and their care is
remarkably consistent among species. Keep the tank clean, don't
overfeed, supply iodine and calcium, and don't overcrowd them. That's
Re: Fiddler Crab questions - a few more.... 12/30/12
Thank you SO much for your information and answers to my questions!
To let you know the few changes I have made since my last email and a
few new questions which have popped up....first the updates on your
1. I have added some salt to their
water so that it is about SG 1.004 to 1.005. I purchased marine
aquarium salt from Petco. When I went there, the employee
suggested regular aquarium salt, but I said your suggestion was marine
aquarium salt so that is what I wanted. The employee told me the
regular was cheaper and would work just as well but I said I wanted to
do things right!!!
<You were correct to buy marine aquarium salt. The chap in the pet store
was very wrong.>
2. Neither have molted yet, but I am not
worrying too much. The only reason I would like the male to
molt is because when I purchased him he was missing one limb and so I
would like him to regrow that!!!
<Crabs moult periodically, but the interval between moults gets longer
the older the crab. So while a juvenile might moult every week or two,
adults may take months between moults. A calcium-rich food source (for
the shell) and a source of iodine (to ensure moulting happens properly)
will both be useful additions.>
3. I bought Sushi Nori and Krill. The
Sushi Nori didn’t go over so well with either of them.
<Like vegetables and children; they may not enjoy it, but it is good for
them. But any other iodine-rich food will do, and if you're adding
iodine to the water, then it doesn't matter too much.>
However, the krill went over fabulously!!! They both LOVE it.
The first time my male came into contact with it, he treated it as an
enemy with his large claw up. My female, well, every time krill is
put in the tank, wherever she is, she will slowly move, eating sand
along the way, acting as if she is doing nothing at all, and sometimes
it will take her 15 minutes to get to the krill, but once she gets to
it, she grabs it and runs to her hiding spot in under the chest in the
water. It is hilarious!
<Sounds it. Do also try things like banana (which some crabs love) and
bones from any fresh fish you eat (just let them pick at them).>
4. I tried to loosen up the sand for them to maybe
make some digging areas, but they seemed to hate the loosened sand, so I
packed it down again. I think they didn’t like getting it all over
themselves, or so it seemed. Oh well.
5. The male’s eye seems to be better in the
water and on land. I guess the brackish/salt water thing worked?
Now for the questions:
1. Now that the water is brackish/salty,
they seem to both spend almost all their time in the water. I made
sure to create a half-half land water situation but no matter what,
every time I look, they are in the water. The only time they come
out is to sit on the chest or if I put krill on the sand, they will come
out to get it.
<What's the humidity of the air like? And the warmth? If it's cold in
your house (which for these animals, means an air temperature much below
22 C/72 F) then they will prefer to stay underwater where (I presume)
the water heater is. Likewise if the air is dry. A fairly tight-fitting
pane of glass atop the tank can keep warmth and humidity in, though do
leave some small gaps for air to flow in and out, otherwise fungus
becomes a problem.>
2. After going through numerous filters, I finally
decided on a sponge type filter. However, it wasn’t doing the best
job. A Petco employee suggested purchasing mesh bags and loose
carbon/zeolite blend instead of the sponge. I did this and it did
wonders for the water as far as keeping the smell down to a minimum and
keeping the water clear. However, on the second change of this
mesh baggie/filter media combination something must have happened
because I noticed the sand started turning a grayish color. Upon
removal of the mesh baggie, I assume there was a tear or something as
the baggie was blackened. My question is - (a) should I be using
this mesh baggie/filter media thing in the first place?
<Zeolite removes ammonia from the water directly, though it needs
replacing every week or so. After a couple of weeks it is saturated with
ammonia and no longer does anything special, and may as well be gravel,
since all it does from here onwards is hold the bacteria that filter
water. Carbon removes dissolved organic chemicals, typically those that
give "old" water odd colours and smells. It also removes iodine, which
is dangerous in this context because we commonly add iodine drops to
crab aquaria to ensure the crabs moult properly. SO I would never use
carbon in this sort of aquarium unless I was providing iodine through
diet, and sure the crabs were consuming that iodine source. In any case,
carbon needs replacing every 1-2 weeks as well. Bottom line, I'd not use
either in this aquarium. Your sponge filter might take a while (six
weeks) to become fully mature and if the air pump is really small, the
amount of water it processes per hour mightn't be that great. A small
internal canister filter could be just the ticket. The Eheim Aquaball
series is inexpensive and very reliable, but you can find lots of other
brands/models. Aim for something that offers a turnover rate around 6
times the volume of water in the tank. So if there's 10 gallons of water
in the tank (which would be about right for a half-filled 20 gallon
tank) then you want a filter rated at 60 gallons/hour.>
(b) do I need to do a total sand change because of the carbon “leakage”,
since the crabs eat the sand? I have made sure to put a fresh
covering of sand in since this happened but obviously the sand shifts
and such, and I don’t want anything to happen so I will do what I need
to do if the sand (carbon) is dangerous….
<Carbon is harmless. No need to remove spilt carbon.>
3. You mentioned to not overcrowd them. Do you
mean as far as with “ornaments”?
<No, with regard to the crabs. Males are territorial, and too many might
fight. To be fair, this is more of an issue with crabs generally.
Fiddler Crabs don't usually fight much, preferring displays, but I'd
still be cautious about stocking. Outnumber males with females, don't
have just two males (they will likely fight all the time), and provide
plenty of climbing places so crabs can spread out when they want.>
I have since taken out a few things. One of my fears is the male
will not have an area to molt since I read they molt in water and have
watched a video of them molting (it looks horrible!). Should I
give them back more water space and less land since they seem to enjoy
<Try it, and see what happens!>
4. Is it typical for the male to do his waving the
claw thing for hours on end all the time every day?
He didn’t do at all until I got the female and now he seems to do it
(especially with the water clear) every time I look at him. On the
chest, in the water, out of the water, under the bridge, on the bridge,
in the chest, under the filter, sitting on the heater, you name it!
It seems like that claw would be difficult to lift since it is as big as
he is or would be tiresome!
<And that's the point. Some evolutionary biology here. As you surmise,
that claw is useless. It costs energy and nutrients to build, it can't
be used for feeding, and it isn't much good for defence either, being
too big to wield or nip effectively. It's basically a handicap. So, the
bigger the claw, the bigger the handicap. Females understand this (or
rather, their DNA has been selected to favour it, which is much the same
thing). Females go for males with big claws, and the bigger the claw,
the more attractive the male. Why? Because for any male to reach sexual
maturity with such a big handicap, he must be strong or fast or clever.
In other words, he must have good genes that favoured his survival. The
female wants those for her offspring, so she goes for a male with a big
but useless claw over a male with a small but useful claw. Needless to
say, males go out of their way to advertise their handicap, in this
case, by waving the claw about in an eye-catching manner. It's the same
explanation for all sorts of male "ornaments" such as peacock tails and
deer antlers -- and I'd argue for men with red sports cars! Such cars
don't have much practical value (expensive to buy and run, difficult to
maintain, don't carry many people or luggage) but they do advertise very
effectively that the owner has resources to spare (which in evolutionary
terms means that person had good genes that meant they did well in
Sorry for the questions again. I appreciate all your answers to my
previous questions. You helped me and my Mr. and Mrs. Crabby so
much! Additionally your information provided quite a few laughs
for me, especially when I watch Mrs. Crabby sneak up on her krill for 20
minutes only to run away with it and hide.
<Most welcome, Neale.>
Re: Fiddler Crab questions - a few more.... 1/3/12
Hi Neale - me again....
Your information prompted a few more questions.
1. I assume you are not from the U.S. as it took me forever to
find the Eheim Aquaball! To be sure, I wanted to ask, is this the
one you are referring to?
seems to be small and not too expensive. Which would you suggest
to use with it?
<It is a good filter. I have one, and generally find Eheim products
reliable and well-made. They're typical German appliances: a bit more
expensive than the Chinese stuff, but on the whole, they last longer and
work better. The only thing I don't like about the Aquaball is the blue
sponge right at the top gets clogged quite quickly. But my tanks are
VERY overgrown so there's likely more gunk floating about than the
average (I like the "wild" look in my tanks so basically let the plants
I have found these two things on that site as well....
<The first is a sponge for another Eheim filter, not the Aquaball, which
uses cylindrical sponges (or, if you do what I do, just fill the
compartments with generic filter wool and/or ceramic noodles). The
second is Eheim's alternative to ceramic noodles. You can use these in
any filter, including the Aquaball, should you want to, though I'd have
thought sponges would be easier to use. For what it's worth, the combo
I'd recommend is the 2208 filter, which offers a second compartment to
the Aquaball, which trust me, is well worth it:
$30 is a fair price for this Eheim model. And here's replacement media
as/when you need it, which shouldn't be for at least a couple of years,
if not longer (modern sponge media lasts years and years if rinsed
On the Aquaball, the top compartment (which is the ONLY compartment on
the 2206 model you looked at first) contains a fine blue sponge. The
2208 has the second compartment that contains a coarser sponge but can
be emptied and filled with ceramic noodles, filter wool, or whatever
else you decide to use. The advantage of two compartments is that you
can "deep clean" one of them while merely rinsing the other one, and
that way, you don't run the risk of killing all the filter bacteria.
Plus, two compartments ensures the filter takes much longer to clog up,
and in my experience, the fine blue filter sponge in the top compartment
gets clogged way too quickly for my lazy fishkeeping! Your own
experience may be different. But for what it's worth, Eheim isn't the
only manufacturer of filters, so if your budget is limited, do feel free
to shop around. I've used internal canister filters from companies like
Rena and Fluval, and while they may not last as long as the Eheim ones,
they can still last many years or more if cared for properly. I will
caution you that "no name" brands like those that come with inexpensive
all-in-one aquarium kits do seem to have a limited lifespan; on one such
aquarium I have, the filter lasts about 4-5 years and I've already
replaced that filter with the same thing a couple times already. Kind of
stuck with it because it slots into a compartment in the back of this
little Mirabello aquarium. Still, for about the equivalent of $40 for a
filter that last 4-5 years, that's still not bad value, even if it is
annoying. The difference is that with a reputable brand like Fluval I
expect a good 10 years, and Eheim units well over that.>
2. Banana - no go! Is there anything NOT to give them?
<Not really. Fiddler Crabs are pure scavengers in the wild, eating the
stuff that washes up on beaches. Algae is also consumed in substantial
amounts by sifting sand, so mushing up some wet fish flake on an
easy-to-clean stone or slate should work well. Otherwise, pretty much
anything is worth trying: bits of fish meat, skin and bones; small bits
of lean raw ground steak; hardboiled egg yolk; squashed cooked peas.>
I have read about zucchini and then you mentioned the fish bone and
banana. I know they are "bottom feeders". I guess I was just
wondering if there were things that is bad for them of if I can try
other fruits and veggies...meats...etc?
<If they don't want it, they won't eat it. Do try serving up food on
flat stones or empty seashells -- these'll be a lot easier to clean up
3. I did wind up changing the sand, not on purpose but because I was
taking out excess food and started to realize the sand smelled. I
figured it had been about two months or so since I had Mr. and Mrs. so
since I had the sand, I wound up changing it. I also guessed it
wouldn't be a bad idea since I had done the water change and such.
Do you have any recommendations as far as how often to do a total change
<Not often. See above on tips re: feeding without making a mess.>
All I can add to this is how thrilled the Mr. and Mrs. seemed with new
sand...they went nuts eating the new sand forever! I assume the new sand
(I purchase a reptile/crab sand) had some good calcium in it or
<Some sand does contain calcium -- coral sand is fine, though reptile
sand will be at least as good, though perhaps more expensive. But as
mentioned above, the "sand eating" is more about removing algae and
bacteria that the crabs actually eat.>
4. You mentioned supplemental iodine. What foods have iodine that
I could feed? Otherwise, what would be a way to ensure they are
getting iodine if not by eating it?
<Iodine drops sold for marine aquaria dosed at around 50% do the trick
nicely. Otherwise, Sushi Nori and other seaweed foods are good, and
there are some crab/shrimp-specific foods that are iodine-supplemented.
Pretty much any seafood (including krill and saltwater fish like
haddock) contains iodine in useful amounts.>
Now for your questions to me...
1. The humidity in the tank - I am not 100% certain; however, I keep
the tank about 80 degrees F. Our house is about 68-70 degrees F.
The tank is always "frosted" or "watered up" so I would assume it is
humid in there. I am always wiping away the excess water build up
so that I can see them in there. The tank I have is actually
completely enclosed in glass with a smaller opening which has a vented
area. It is the Fluval Edge
2. I only plan on having two crabs for now in the tank so no chance for
overcrowding. The reason being the tank size. The tank is
only about six gallons. I figured this was okay for
two crabs? They seem to be fine with each other space-wise.
<Should be okay, but adding another female or two wouldn't be out of
Finally, just a few things I wanted to mention and ask which are not
directly related to the crabs...
1. How did you become a Fiddler crab "expert"? I was fascinated
by crabs since a child (I am a cancer, born in June). Always loved
hermit crabs but was never allowed to get one. I lived in Grand
Cayman for a while and when I would go for walks, I saved quite a few
hermit crabs as they crossed the road. I also saw lots of other
crabs on the island and they were so adorable. I never saw little
crabs such as the Fiddler crabs until seeing them at our local Wal-Mart.
I fell in love immediately. Something about them was just too
cute. My mom was with me and I am living with her right now, but
since I am a 34 year old, she couldn't do much about it when I said I
wanted to buy one! She's fallen in love with them and their
mannerisms now as well. Even a woman she knows in Scotland who
said she didn't like crabs because they looked like spiders and wouldn't
watch a video my mom had sent has now watched a video and is in love
with our Mr. and Mrs. Crabby!!!
<Hmm… not really sure "expert" is the word here, but I did do a marine
zoology degree, and my PhD is in invertebrate palaeontology
(specifically, heteromorph ammonites). Have kept a few pet crabs and
shrimps over the years, a favourite being two or three species of Mantis
Shrimps that I worked on at university. At the moment limited to a
gazillion Cherry Shrimps.>
2. I wanted to let you know that because of my experiences here with
the Fiddler crabs and Wal-Mart, I actually got our local Wal-Mart store
to stop selling the Fiddler crabs. My first experience with the
crabs was a cute little guy I found there and he died shortly after
purchasing him. I thought maybe loneliness or me not knowing
enough. So I purchased a large terrarium set-up and spend a bunch
of money and purchased four males and four females from Wal-Mart...still
not realizing the conditions of how Wal-Mart was keeping them. All
eight of the crabs died within a few days. The worst was a large
male which I stayed up all night with, cried with, as he lost his limbs,
and I tried to hand feed him and put him in the water and out of the
water all night long. Each time it seemed as though he passed, I
would put him close to my face, and his eyes would pop up and look at me
as if to say, "not yet, I'm not ready yet." It was so sad.
He carried on for about 16 hours like this. It was heart-breaking
for me. When I went to Wal-Mart they wanted the crabs to "dispose"
of them. I told them they could not have them because they did not
go through what I did with them and I was going to give them a proper
burial as they deserved with our other animals which have passed.
A few days later when I was at the store, they had more crabs and half
of them were dead in their little Betta containers. After this, I
emailed Wal-Mart and told them how they did not know how to care for
these little creatures, and how PetSmart changed their policies
regarding Fiddler crabs once it was brought to their attention how to
truly care for them. I told my whole story to Wal-Mart in an email
and at the end I said "I am trying to appeal to your heart; however, if
I can't do that, I appeal to your bottom-line, since I know that is what
matters these days. Every crab that dies is costing you money.
So even if you don't care about these wonderful little creatures' lives,
maybe you'll care about the money you are losing." I received a
phone call from the manager and he told me their store would stop
carrying the crabs and he would try to appeal to the Wal-Mart chain
since they don't sell many of them. He said they receive them in
the little containers and are told to display them like that.
<Ah now, the little containers are indeed used for shipping, and with
good reason. Crabs tend to fight when packed in groups, so traditionally
they have been exported in what the trade calls "soap boxes". Of course,
just because they're shipped that way doesn't mean they should be kept
that way, any more than the best way to transport your cat to the vet in
a carrying cage isn't the best way to keep your pet cat at home!>
He said from now on, he would display a sign simply saying they could
order the crabs if a customer wanted one.
<A wise approach. Well done on encouraging this.>
The next time I went to the store, I saw some crabs and was very mad.
Two were dead and the one live one had very little water yet was
extremely active and waving hello to me. I decided he needed a
chance. I was hoping from this point, no more crabs would be seen
at the store and guess what.....No more crabs have been seen at our
Wal-Mart store!!! I am hoping that the manager kept his promise to
try to contact the chain manager try to get them to stop selling them in
other stores. But at least I know I made a difference at our
<For sure. On the one hand, shipping crabs to certain doom in a pet
store isn't really any worse that sending crabs to a seafood processing
plant. Either way, the crab's dead. But yes, there's an ethical issue
here about animal welfare, and live crabs processed for food should be
on ice to minimise suffering, and killed quickly as/when required.
That's a much different thing to a lingering death through starvation,
the wrong water, or the loss of limbs. So well done for what you're
Well, I think that is all for now. Once again, I appreciate all
your help! Thank you for taking the time to read and respond to my
<Been a pleasure. Have fun! Neale.>
Re: Fiddler Crab info.....
Hi Neale - I just had to tell you, even though I don't know you, you
have given me so much super advice...I am super excited.....MY FEMALE
<Very well done to you both!>
All your recommendations must be helping cause I must be doing something
I am awaiting my order on the Eheim Aquaball, as well as a Rena
Smartheater because the heater I have has been somewhat unreliable with
the temps up and down rather than maintaining a steady temperature.
<Enjoy your hobby, Neale.>
Re: Fiddler Crab questions and stuff....
Well, my male molted...he molted in the treasure chest he had been
hanging out in for the past day or so and I noticed today that the
"crab" inside the chest was light in color and realized it was his old
shell. I checked around the tank to find him and saw that he was
missing his large claw :(
<Happens. Will grow back with each new moult. Actually pretty cool to
When I pulled the chest up I could see that it was still stuck inside
the old shell...it fell off him during his molt. This made me very
sad as you can imagine. He did manage to grow back his one leg so
now he has his eight legs back but now only his little claw. Will
he be okay as far as getting around and such?
I assume now I have to wait until his next molt for him to get his claw
I will miss Mr. Waving Crabby. He used the big claw for holding
some krill and such when eating so now I am afraid for him.
One second concern of mine is that I've done, I think, two or three sand
changes and WOW does that sand STINK!!!! I mean stink so much that
you have to open up doors even though it is -20 degrees outside just to
air the house out, plus light 20 candles, hold your nose, and try not to
vomit stink. I thought it might be the carbon I was using in the
filter media bags but I stopped using those and it's still happening.
<Sand will develop anoxic decay, and yes, it's pretty foul. Normal, but
foul. One approach is to minimise the quantity of sand. You can also
fold in a lot more chunky stuff like seashells, gravel or coral rubble
to "open" the substrate up and allow oxygen in.>
I did get the Eheim filter but the problem is that my water is not deep
enough for the filter and the filter is also too big for my tank.
I am going to have to search out another type of filter. The Rena
Smartheater is doing very well though at keeping the temperature and
humidity much more stable. It takes up a bit more room than my
other heater but it has a light that lets me know when it is heating up
vs. when it is stable, etc. I think that has helped some but the
smell is pretty nasty so I have to figure out what to do with that
Re: Fiddler Crab questions and stuff....
Do you think this would help keep the smell down and would it be
appropriate for the fiddlers?
http://www.livesand.com/ It mentions something about
preventing "biofouling". I just don't know if it will work as far
as the bacteria it contains as well as the "salt" content and if it
would mess with the SG and salinity.
<The bacteria in this sand may not adapt to brackish conditions, though
in theory, they should be okay down to about SG 1.005. Would I bother?
Probably not. By now your sand is as rich with bacteria as any -- that's
why it smells. The problem is there isn't enough oxygen getting down
deep into the sand, so there's anaerobic (= smelly) decay. Anywhere the
sand gets deeper than an inch, this will be a risk. Live plant roots and
burrowing snails (like Melanoides spp.) help prevent this problem a good
deal, but in your tank, neither may be options (though Melanoides can
tolerate brackish water to SG 1.010, so might be worth a shot).>
Otherwise, I found these
Would these work better than the live sand at reducing the odor?
<Possibly, but at $38 a pop, they're hardly economical! All you have
with these is some sort of pebble-like substrate with lots of cracks in
each grain, so the amount of bacteria it can hold has been improved
compared to regular gravel. For what you want, the removal of anaerobic
decay, the aim is a substrate with more burrows for air to travel down
from the top to the bottom.>
I've been using reptile sand which is about $1/pound and the crabs seem
to enjoy it the best as far as eating it and such; it does smell and get
expensive...and it is a pain to wash every time!!! Since we keep
the crabs in our main living room, the smell is the worst part so let me
know if either of the above options would work better or what you would
recommend as a suitable option for a sand replacement which is similar
to sand but doesn't have the negative aspects associated with it.
<I would remove ALL the sand. Decorate the tank with rocks, bogwood, and
plain gravel. Now, somewhere in the vivarium make a shallow area where
you can insert a bowl of some kind (needn't be an actual bowl, just
something plastic that's around an inch deep). Fill this bowl with sand.
Let the crabs mess about here, and as/when required, you can easily
remove the bowl and clean the sand. Basically, it's a cat litter box for
I know you said Mr. Crabby will be fine without his large claw but it is
really sad to see him doing his waving all around with just the itty
bitty claw.....and still trying to be impressive....
<Hope this helps, Neale.>
Re: Fiddler Crab questions and stuff.... 2/3/13
Hi Neale :)
Thanks for your feedback on the live sand and the pebbles. I think
you probably saved me some money there! I am understanding why the
sand is smelling now and if it wasn't for you, I would have no clue!!!
When I first had the initial crabs that passed away on me I used gravel
and come to think of it, there was less smell. I went to sand
because I heard crabs liked sand better.
<They do. But you only need enough for them to feed in, so a bowl will
I wanted to do things right by these guys so I switched to sand.
They seem to love their sand so much and I hate to take it away from
them and just put a small bowl out.
<They'll adapt, especially if you put food elsewhere for them too, so
they use the whole tank. A bit of ripe banana or raw fish smeared onto a
pumice stone or bogwood root for example would give them plenty to keep
Tell me if this would work - put all gravel in the shape I have the sand
in now, then put about an inch of the reptile sand over the gravel?
<Sand will sink into the gravel, so trying to layer them won't work. Try
embedding a shallow plastic dish (like the kind ready meals come it)
into the gravel. Something around 15-20 cm/6-8 inches across and 2.5
cm/1 inch deep would be ideal. You could even get really creative and
use silicone to glue gravel and rocks to the outside, so it's decorative
and doesn't show up too bad. Then fill with sand. Easy to clean whenever
This way there wouldn't be all sand and Mr. and Mrs. Crabby would have
their sand like they are used to having. Would that cut down the
odor or would the sand sneak down into the gravel and eventually create
odors? I figure worst case scenario is that gravel is cheaper in
the long run and if I have to change things more often, I am either
changing the top level of sand which is less sand to change or I am
changing the gravel and sand which is probably cheaper.
Oh, and as I said, the Eheim filter did not work for me, so I wound up
ordering this filter instead, let me know what you think....
Same one just a different description:
It has two sponge type filtration plus a place for adding a substrate
(carbon or whatnot). It is smaller and can be in less water and I
can mount it horizontally or vertically....this was the challenge with
the Eheim….I didn't have enough water for it to be submersed fully...as
I only have about four to five inches of water.
<And you couldn't put the Eheim on its side?>
I appreciate all your input!!!
Re: Fiddler Crab questions and stuff.... 2/11/13
Hi again Neale,
So, you were right about the coral and sand thing. I wound up
having to clean and drain coral of the sand - not fun!! But this
time I put a barrier between the two to minimize the mixing of the sand.
One interesting thing though which I have to ask you about is this -
While I had the crabs out of their aquarium and in their temporary
set-up while I changed things, my mom checked on them and notice that
the male had the female backed up against one wall with his arms around
her. She told me they were mating. At first I didn't believe
her but then after about 15 to 20 minutes or so of them being like this,
I looked it up and started to believe her. So, now I ask
you.....were they in fact mating?
<Likely so. Males "straddle" the females, wrapping their legs around
In the wild this happens immediately after the female has moulted, the
male both protecting her (she has a soft shell now) as well as
fertilising her eggs (which he can't do when her shell sets hard).>
Did they have enough time to breed or will they actually breed now?
<Mate yes; breed successfully, unlikely. Fiddler Crabs produce
planktonic larvae that likely won't survive long in aquaria. Even if you
get salinity right, filters generally hammer plankton.>
The female didn't look any different and they aren't acting any
differently now that they are back in their original tank. My assumption
was they typically didn't mate, breed, spawn, have babies, etc. in
captivity so I was very shocked by their behavior!!! Should there
be anything for me to be looking for at this point?
<Not really. Put it down to an interesting experience to watch.>
I thought this would be the last question I'd ever have to ask!
<No problems. Cheers, Neale.>
Re: Fiddler Crab questions and stuff....
Okay, well, no doubt they mated - as the since I put them back in their
tank with the filter on, the female was staying out of the water - her
favourite place to be. After your email, I turned the filter off
and checked took out the hiding log and sure enough her belly is reddish
and different looking.
<Likely the eggs, if the "red stuff" looks like tiny bunches of grapes.>
Sooooooooo, now what?
If I wanted to try to get her to have baby crabs what would be the best
way to try for a possible positive reproduction. I know it is
highly unlikely but is there anything I can do to help?
<Yes. The mother will carry the eggs for some days, but when they hatch,
she will dip into the water washing the planktonic larvae into the sea.
Under aquarium conditions this is somewhat easy to accommodate, insofar
as the mother will take care of the eggs until they're ready to hatch. A
motorised filter will obliterate any larvae though, so you're limited to
air-powered filters, ideally a simple sponge filter.>
As I said, I know highly unlikely but it is just so interesting to
me!!!! I never thought this would happen because I read that even
breeding in captivity was basically non-existent.
<There was a report of breeding for Red Claw Crabs (Perisesarma bidens)
online, but sadly it's down. It would be very similar to Uca spp.
(Fiddler Crabs). The basic idea is you need marine infusoria ("green
water") for the larvae to eat, and it takes some weeks for the larvae to
pass through the various moults until they become teeny-tiny crabs that
settle out on the substrate. In theory, once that happens, the crabs
will be a lot easy to rear.>
Now that it happened, well, I'd like to see where it could go. Unless
you tell me it would be a bad thing to happen - like I don't want to
have 100 baby crabs or something.
Can you tell me a bit more on their reproductive cycle and breeding,
mating, what happens, how they have babies, etc?
I tried to look it all up but there is so little info on Fiddler crab
reproduction since it simply says in captivity it is unlikely so I just
didn't think it would occur and am sooooooo confused now.
<Hope this provides a little help, Neale.>
Re: Fiddler Crab questions and stuff.... 2/12/13
So the suggestion would be to leave everything as is for right
now....except get a sponge filter.
<Pretty much. I wouldn't spend much money on this project unless you
really are bitten by the bug. If that's the case, you may want to try
something more ecologically rounded… a wide, shallow tank; an air
bubbler for movement; couple lumps of live rock to "seed" the water
column with plankton; plus of course some seawater. You can add the
crabs to an aquarium like this. They will happily bathe in seawater, and
crawl back out again when done… Uca spp. are fully euryhaline,
In a few days, Mrs. Crabby will come out from her hiding log and get rid
of the eggs.
What happens then?
Do I keep the eggs in the same aquarium as Mr. and Mrs. Crabby?
How long does it take for the eggs to hatch?
<To hatch, likely less than a day; to metamorphose from newly hatched
larvae through to mini-crabs… some weeks. Not sure this data exists for
Uca spp; use Google Scholar or similar.>
Any special prep for the eggs to hatch?
<Expose to seawater.>
Will ALL the eggs hatch?
<No idea at all. There's really no hobby experience of this. Indeed,
breeding crustaceans with marine planktonic larvae (e.g., Amano Shrimps)
is very hit and miss.>
Obviously I wouldn't mind having a few babies, but it scares me to have
100's of babies!!
<Not much chance of this.>
Once the eggs hatch to larvae - what is green water?
<Water exposed to light and teeming with algae… like you see in
How do I create it?
<Marine aquarists have access to marine algal starter cultures… do see
"marine infusoria" and "marine aquarium phytoplankton".>
Do you think it is likely that I could actually get some successful eggs
to hatch and larvae to grow into crabs? What is the likelihood of
<Likely less than 1-in-100, but doable if you were dedicated. Do read up
on breeding Amano Shrimps: it is difficult, but doable.>
<Good luck, Neale.>
Re: Fiddler Crab questions and stuff....
So, the other night, Mrs. Crabby came out of her hiding log and went
under the bridge. I figured it was time for her to release her
eggs. I wanted to capture it on camera so I sat and watched.
Well, three and a half hours
later, I realized it was not going to happen. This is what took
She went under the bridge where there wasn't complete water coverage.
I turned off the filter. She sat under there for the longest time.
Finally, she started to pick away with her claws at the front of her
She would take a break and then start again. When she would stop,
it would look almost like she would contract her belly and then she
would start picking again. I thought perhaps she was cleaning off
some sort of sack to help release the eggs; but I realized she wasn't in
the water completely.
After watching this for - as I said - three and a half hours....I
realized she seemed to be "eating" away at the eggs. Could this be
what she was doing?
<If she was messing about with them using her claws, she might have been
eating them, but this is also how they push the eggs into the sea just
before they hatch.>
I finally gave up watching. The next day, it looked as though she
still had eggs; however, she was acting more "normal" as in going in the
water, climbing around, etc.
Any ideas on what happened or what is going to happen?
Did she eat some of her eggs?
It looks like she still has some eggs, but is acting normal (yet
sometimes still hiding out like she did for those few days) so what is
going to happen to the leftover eggs? Is she just going to eat
them all eventually?
<Maybe. Female animals will often "recycle" the energy put into
offspring if they feel conditions doom their offspring. Sounds grim, but
makes sense from a Darwinian perspective where the female who uses her
energy wisely will be the one who leaves the most descendants.>
Will she release some of them at some point?
<Should do. But little is known about reproduction of Uca spp. and
nothing at all about their breeding in captivity.>
<Keep observing, and do remember you're a pioneer here! Cheers, Neale.>
Re: Male molted
Well Neale - Mr. Crabby molted and got his BIG CLAW back!!!!!
I went to clean the tank today and picked up the bridge and saw Mr.
Crabby and his molted shell. So I put the bridge back and decided
to the cleaning could wait a few days :-)
<For sure. They can be a bit delicate for a day or two after moulting
while their shell hardens.>
Just wanted to let you know that update. Not sure what is going on
with Mrs. Crabby though as far as the eggs. She's been in the
water for the past few days hanging out.
<Hmm… just leave her be. Producing eggs is "hard work" and does deplete
the energy store of the female crab, so you want her to rest up between
batches, and get lots of good meals.>
Doesn't look she has eggs any more but hard to tell.....
<Thanks for the update, and good luck! Neale.>
Re: Male molted 3/5/13
Hey Neale, one thing I forgot to mention is that I thought when males
lost their big claw, and they molted, it would come back on the opposite
side....however, my Mr. Crabby's big claw came back on the same side!!
<As it should…>
Is this because he lost the whole claw and joint during his last molt
rather than just losing the "claw" part?
<Genes, I think; likely Uca spp are "handed" like we are, using either
left or right for display, but not both, depending on the species.>
I was expecting the opposite side to have a claw and it was the same, so
I was surprised!!! We are so happy that he has his claw back
though. He seems to be not using it all that much (no waving
waving waving yet), but seeing him waving that little thing was just
difficult to watch.....
We are hoping maybe him getting his big claw back will prevent them from
"getting busy" again. It seemed like they only mated when he lost
his claw. If it happens again, we may have to think of getting
another female so it doesn't take so much energy out of her!!!
<Quite so. But if all else fails, make sure "mom" has lots of protein
and calcium rich foods… frozen krill and brine shrimp, little bits of
fish with the bone in, even things like sardines mashed up with bones
and divided out into tiny little portions.>
Re: Female Fiddler - with babies again?!
So, after the whole thinking the female ate her eggs, it seemed like
Mrs. Crabby was acting semi-normal....e.g. she was in the water, eating,
hanging out by the heater, etc. I looked in on her a few times and
it seemed to me it looked like she didn't have any more eggs left.
I never saw any eggs anywhere in the tank or anything though.
Anyway, she acted like this for a week or so and then for a few days I
realized I hadn't seen her and had only been seeing the male hanging out
in the water. Usually she stops hanging out in the water if the
water isn't to her liking (not warm enough, dirty, etc). But the
water seemed fine. I got worried so I searched around for her and
lifted up the log on the land area and she was in there and went into
the water. I immediately noticed - a dark red belly!!!!
<More eggs perhaps? Should be obviously so, if they are eggs.>
So now, questions again from me.....
1. Is it possible I was wrong for those few days and she somehow
had the eggs but I couldn't see them?
<Very. They don't carry the eggs for long, perhaps a few days, and once
shed, they often disappear into the filter.>
2. Is it possible they mated AGAIN???? So soon????
3. Is this going to be a recurring thing now????
4. THIS IS CRAZY!!!!! - okay not a question - just frustration and
I thought, okay, breeding in captivity once - lucky chance and an
interesting thing. But now twice? Is it good for her?
Especially since she will never have viable hatchable eggs (and will
probably eat them again)?
<Spawning and breeding are two distinct things. Many crabs will spawn
regularly in aquaria. But successful breeding is very rare.>
Do crabs have "feelings" like maternal feelings, I mean, does this have
an effect on her well-being?
<Crabs have no maternal feelings at all; at least, not the ones that
shed the larvae into the sea, leaving the larvae to drift away to
I'm sure there are some crabs that extend some degree of broodcare, but
I don't know of any that are traded.>
If this keeps happening, is there a way to stop it? I miss seeing
my Mrs. Crabby!!! All she does is hide out in her log now!!!
<It may well be that if there's a male in the tank, mating will happen,
and there's not much you can do to stop that. Adding additional females
could make life easier for all the females in the tank, but I doubt it'd
stop them going into "berry" as it is called when crabs carry their eggs
Re: fiddlers - a few things
Hey Neale -
So, since the male molted, he was looking really light colored, then I
realized, I hadn't given krill for a few days...amazingly, I gave some
krill today and within hours, his shell was back to its dark color, his
limbs back to dark and his big claw started to darken!!! It was so
crazy that just the little bit of krill could do all that!!
<Not so crazy. Crustaceans (and indeed many other animals, including
fish) synthesise red pigment using (as chemical precursors) a substances
that we loosely call the carotenes. True carotene, or beta-carotene, is
found in plants (famously, carrots) but similar proteins are in
crustaceans, including krill. These carotene-like proteins are the ones
that turn crab shells pink when cooked, and they're also the ones in
brine shrimp that make flamingos pink! Put another way, krill can and
will provide chemical materials that animals will use to synthesise skin
and shell pigments. This said, do bear in mind shells change colour
through the hours immediately after moulting during the chemical
processes that make the shell hard.>
On another note, Mr. Crabby got busy with Mrs. Crabby
AGAIN!!!!!!!!!!!!!!! Yes, she is carrying more eggs! It
seems like it is only about two or three weeks in between...if that.
I will look in and she is not carrying eggs and I will look in again and
she is carrying eggs. It is ridiculous! Do you think getting
another female would help? Will Mrs. Crabby be okay with a
mistress? Will Mr. Crabby leave Mrs. Crabby alone and go with the
<Yes, adding more females is almost always a good idea with any animals
where males mate indiscriminately… if for no other reason than it means
the male can't be "getting it on" with one female ALL the time; at
worst, he shares his time out among his harem of females.>
Another thing is regarding how you mentioned that it was no surprise to
you Mr. Crabby’s claw came back on the same side. I had read on
numerous sites that it would regenerate on the opposite side, which is
why I was surprised it was on the same side. I guess all the sites
are wrong huh J?
<Not really. The thing in biology is that few rules are set in stone.
Most humans are right handed, but not all. Most humans can't hear bats
squeaking, but some can (I'm one, and only very slightly). Most humans
grow wisdom teeth, but not all. And so on. So while it may be more
common for Fiddlers to regrow one claw rather than the other, it might
not be an "always" thing.>
Also, between molts for Mr. Crabby, there was only one month between his
molt where he lost his big claw and the one where he got it back...do
you think he molted so quickly because he lost his big claw?
<There might be some connection, but I don't know. You could speculate
though that evolution would favour males that "got back into the game"
quickly if they lost a claw, i.e., moulted a few times to grow a new
one, since those males would the ones most likely to sire offspring,
compared to any males that conserved energy and moulted at more
Can Mrs. Crabby molt with all these eggs she is carrying seemingly
<Likely so, but at some cost… would try isolating the male at times, if
at all possible (though admittedly tricky with amphibious, climbing
animals like these). Else make sure she feeds very well… fish fillet,
krill, softened fruits, raw beef mince, hard boiled eggs.>
Or will she molt between when she is not carrying them? I am
assuming it is probably time for a molt since she molted prior to Mr.
Crabby’s first molt. I’m not worried about her molting per se, but
more so constantly carrying eggs. She isn’t as fazed by them as
she was the first time, as she basically does her normal thing now as
for hanging out in the water, climbing on stuff, etc. She just
does it all with all those eggs in her belly area - which has to be
heavy for her size...Additionally, she picks at them and seems to eat at
them at her leisure or do something with them..not sure and then one day
they are just gone...
I guess questions -
1. Did the krill really work that fast for Mr. Crabby in
turning his shell color?
2. Can it be possible Mr. Crabby is mating with Mrs. Crabby
3. Will another female stop Mr. Crabby from mating with Mrs.
Crabby so often and have him mate with the other female and will Mrs.
Crabby like/dislike the new female?
4. Is carrying eggs preventing Mrs. Crabby from molting?
<Unlikely, but I don't know.>
5. Is it bad for Mrs. Crabby to be eating the eggs all the
time - as she doesn’t seem to eat much else then?
6. Can this be bad for Mrs. Crabby’s health overall?
7. Any other advice?
<Do make notes on what you observe… long term, little recorded on
successful maintenance of Uca spp.>
Thanks so much Neale!!
<Most welcome, Neale.>
Re: fiddlers - a few things
Thanks for your response Neale!
You said to make sure Mrs. Crabby eats well; the problem is, she doesn't
eat at all while she has the eggs. I have noticed this batch of
eggs seems to be hanging around longer and she seems more listless each
day. It has me worried. The eggs don't seem to be going away
as fast as the last few batches. She just is sitting under the
heater. Today she wasn't moving about so I actually had to open up
the tank and move the heater to see if she was living....that is how bad
<Indeed. Do consider isolating the female for a while… some weeks,
couple months. If this is a draining experience, she may be becoming
stressed by it.>
Regarding the krill thing - Mr. Crabby's shell was light for about four
days - almost translucent, even though I was feeding shrimp pellets and
other crab pellets, etc. His big claw was also white to
translucent. I was very worried about him as he was not darkening
after his molt at all. After I did a tank cleaning and put the
krill in, he ate some and it was like watching magic at work.
Literally, his shell changed color right before our eyes. As we
watched (my mom and I), we were amazed to see the color start to go into
his big claw. The big claw is still translucent to white at the
end but the transformation from molting, then three or four days of him
being super light in color (his shell, his legs, etc.), then giving the
krill and seeing him transform to a dark shell and dark legs and
semi-darkened big claw within less than an hour was simply crazy!!!
As we watched, we literally saw the color go up his "arm" of his big
claw and into his big claw. I was so mad I didn't give him krill
after he molted!!
<May or may not be related… keep an open mind.>
Well, from everything we have discussed, it sounds like my tank needs
another female (a mistress in the tank....Oooh). How do I
introduce her into the tank - just plunk her in?
<I would remove the male, add the female, let her settle in, then
release the male. Keep him in a bucket, "critter container", or
something he can't escape from.>
I am assuming around my town I will be getting her from a tank where
they keep them in a completely enclosed freshwater tank; will this
matter how I introduce her to my land/slightly salty water tank?
<Salinity will not be a factor, no; Uca spp are euryhaline and
amphibious, and able to dip into whatever salinity they come across,
with the proviso that indefinite denial of brackish or salt water seems
to be harmful.>
Does it matter as far as introducing her to the male first or the female
first or just putting her in with both of them at once? Should I
look for a small/younger female or a slightly older female - I highly
doubt I will have much say in this as fiddlers are few and far between
around here...but if I have a choice, which should I choose?
<Would get specimens of similar size.>
Thanks so much again Neale. You are so amazing!!! Thanks for
not getting bored with my questions!!!
<Not bored; learning from your experiences. Cheers, Neale.>
Re: fiddlers - a few things 3/23/13
Well, the update is that I got two new females, one is about the size of
my current female and the other is just a bit smaller. I tried
separating out my female but she seemed miserable being by herself.
I decided I would try them all together and see if the male leaves her
alone. We'll see how things turn out.
The two new females were from Petco where they keep them in freshwater
tanks all the time. They got them in today though. The new
girls took to the new semi-salty tank right away and started to eat away
at the sand and food stuffs - krill and brine shrimp. Once they
got used to the tank, I put my female in and watched to see how she took
to the new girls. After that, I put the male in. So far so
Let me know if you have any advice if you think I am doing things
<No Jennifer, I think you're doing everything that's reasonable and
appropriate. You seem to have a good grasp of the basic issues like
salinity and diet, and with luck, adding extra females should balance
out any social stresses more evenly. Good luck, Neale.>
Re: fiddlers - a few things 3/23/13
Well - Mrs. Crabby didn't have eggs so I figured it was a good time to
add the new gals. Guess what - Mr. Crabby got busy with Mrs.
Crabby last night and she has eggs again!!!
<Ah, well… Overall this is a good sign; if conditions weren't right,
they wouldn't be breeding so much.>
Since Mrs. Crabby didn't like being by herself, would be it a good idea
to put Mrs. Crabby with the smaller female in another tank for company?
This way Mr. Crabby would have the bigger female (who is actually bigger
than Mrs. Crabby), and Mrs. Crabby would have someone as well. It
is just an idea I had because I know both Mr. and Mrs. are used to
having company. Let me know your thoughts.
<I'd tend to leave them all together in the one tank. Spreads out the
male's attentions, and the male should ignore the female carrying eggs
anyway. On the other hand, crabs don't really need company so far as we
can tell, so if you want to isolate one, don't feel the need to add a
companion; she'll be fine alone.>
One cute story to share with you is that when I had all three females
in, and then added the Mr. he acted hilarious! He first went into
the water but then realized there were more females and ran up onto the
land and into the cave. For about 5-10 minutes, he proceeded to
"pace" within the cave, outside the cave, peek from one end outside of
it, go back in, come out the other side and peek out, go back in, pace a
bit within the cave, etc. It reminded me of a male trying to
figure out what to do when he wants to approach a new girl but not sure
how to do it.
<Probably very similar behaviour. Do remember that male crabs run the
risk of being attacked by other males as well as larger females, and
anywhere that looks attractive to him as a potential home could well
attract another, bigger male he'd prefer to avoid. Likewise any group of
females he's interested in will pique the interest of other males, as
well as any predators, so he'd want to approach a new group of females
My mom and I were laughing so hard the way he acted. He almost
came out a few times but decided not to. Finally, when he decided
to come out of his cave, he slowly came down, and approached the larger
female. She didn't seem to mind. He moved a big closer and
he waved his large claw in small motions really quickly. As she
moved away, he followed slowly but didn't make too many motions, just
followed her. At one point, he did check out the smaller female
but she scurried from him and he left her alone and kept his attentions
on the larger female...until he decided at some point to go "knock up"
Anyway, I just wanted to share how cute the Mr. was with the new
females. I also wanted to ask about what to do regarding the
separation and if putting another female with the Mrs. would be an
<I'm glad you're enjoying these animals. They're much misused in the
hobby, and when kept as freshwater crabs, rarely live for long. Clearly
your specimens are providing you with much entertainment. Before long
you'll be thinking about keeping Mantis Shrimps, I have no doubt…!>
P.S. Glad you are not bored with my emails!!!
<Indeed not. Cheers, Neale.>
Re: fiddlers - a few things 3/28/13
Mr. Crabby has been busy...he not only knocked up Mrs. Crabby that first
night...but now he also knocked up the smaller new crabby. He
hasn't done anything with the bigger female as of yet. Maybe she
is too intimidating or won't let him - not sure. So my tank has
two females with eggs, the male, and the larger female.
I am getting a second tank. I know you suggested giving Mrs.
Crabby a break. I may still do that.
I am glad that the water conditions and such are so great for mating;
but geesh, I had no clue that Mr. Crabby would be such a, well, horny
little guy. He wasn't this way at all until he mated with Mrs.
Crabby the first time. Now it seems that is all he is doing and
wants to do.
<Nature. Now he knows food is 'on demand' and there aren't any
predators… well, his mind focuses on procreation.>
It was so much easier and fun when there was no mating going on.
Mr. Crabby sits on his chest and waves his claw nearly all day long -
must come down to mate at some point. The girls with eggs hide out
in the cave or by the filter. The larger female is usually under
the heater or if approached by the male (or me) runs away. One question
I have for you is about color of shells. When I got the two new
girls, both were very "orange-ish" brown in color, vs. my two were very
dark, deep brown. Is this due to the salinity of the water?
Is it due to diet? Is it due to molting/being close to or not
close to molting?
<Could be any/all of the above. Hard to say. Provided the shells aren't
soft or fungused, they're likely fine.>
Again, thanks for listening and your advice!!
<Do consider joining the WWM forum… do think others would enjoy
discussing your experiences. Have fun! Neale.>
Re: fiddlers - a few things
A quick update...and of course, a few questions...as always…
Mr. Crabby is definitely happy with his "harem". All three girls
are constantly with eggs now, with the exception of when they dispose or
eat them for a day. I feel bad that they are always with eggs - is
this something they are "okay" with?
<In theory it should be fine, but with the proviso that the energy
expended on making the eggs is offset by a rich, varied diet that
ensures the crabs don't lose "condition". Keep a close eye on feeding,
and if you can, isolate the male periodically, perhaps using a breeding
trap or something. Even if the male can be kept away for a few hours
each weekend, that'd be enough to ensure the females get a good feed,
perhaps a whole lancefish or unshelled prawn to themselves. You could
also turn the heat down a couple degrees, as this should dampen his
ardor, but not too far… maybe down to 22 C/72 F, and see what happens.>
It doesn't seem so, as it seems they try to stay away from him by
huddling under the heater or crouching by the filter. They are
very inactive overall and seem to stay where Mr. Crabby can't get to
them. This makes them stay virtually on top of one another.
When I cleaned the tank, I put the three girls into a separate tank and
they were relatively active for a while and then they played Queen of
the castle and tried to get the top of the decoration I put into the
separate tank. Since I didn't want fighting to ensue, I took that
decoration out and put one in without a definitive "top" to it.
This ended the fighting. While the three girls were by themselves,
Mr. Crabby was by himself in a separate tank and he basically his in a
small corner behind a small rock dish area the whole time. Let's
just say he was VERY happy to be reunited with his girls after 3-4
hours. He waved that claw so fast and stood on his tippy
tippy-toes on the heater for hours.
<Try looking out for some mesh or egg crate you could use to create a
Since the tank cleaning, I put the filter closer to the wall and to the
bottom of the tank, thus taking away the space where the girls were
huddling and hiding...I am not sure if this was a good idea or bad one.
I would like them to be more active within the tank, but I don't want
them to feel they have no place to go and hide from Mr. Crabby.
<Hope this helps, Neale.>
Re: fiddlers - a few things 5/28/13
Been a bit...things are going alright with the crabbies....I guess I am
getting the hang of things overall. I am still finding new ways of
doing things and trying to figure a few things out though. Of course one
issue is still the sand/gravel thing. I finally decided that since
my crabs seem to like the water more than land and don't like to burrow,
<Odd this, because the crabs are meant to be amphibious, and are so in
the wild… but in aquaria, it seems that they often become more aquatic;
perhaps the lack of warm, humid air dissuades them from their
I needed to do some inventing. I bought some Plexiglas, silicone,
gravel, and sand....took some measurements....got the Plexiglas cut and
then built a sort of "invisible" platform in the water. It
consists of a bottom, back, top, on longer side, a middle piece for
structure, and then a ramp piece. On the ramp, I siliconed a bunch
of gravel down and I siliconed all the other pieces together. Once
finished, I put sand on the top piece, as well as the ramp (the gravel
was to hold the sand on), and then a bit of sand around the bottom of
the tank. I added some more hiding areas into the newly created
spaces from the Plexiglas, and then filled it all with water.
Basically my tank was being half used up by a sand pile which was
rotting away weekly. Now, I created a situation where the whole bottom
tank is filled with water but the crabbies can escape (just like always)
out of the water by going up the ramp and to the platform area.
They really didn't lose any land space, but they gained a ton of water
space. They seem to like it quite a bit.
<I bet. You're quite right to experiment; oftentimes the animals don't
care if their enclosure isn't "natural looking" provided it satisfies
their demands. If you think about it, we humans aren't much different --
our homes don't look much like the open plains of Africa, yet that's
precisely what would be natural for us!>
Mr. Crabby took a break for a while from getting busy with the girls - I
think it was because he had to molt. He successfully molted and
his claw got quite a bit larger and he was very cranky for some time
prior to and after his molting. After he got over that, he mated
with two of the females....grrrrrrr.
I have also found some pellets that don't seem to make the water as
dirty. They have some seaweed component as well as a shrimp
component. I also feed them frozen krill (and some freeze-dried
krill) at least once a week. I usually have to turn the filter off
otherwise it all heads towards the filter immediately. They all
love their krill!!!! Sometimes one of them will get goofy and go
around trying to collect all the krill from around the tank - as I try
to spread it around so each can have access to some.
<Good source of calcium, presumably.>
I found a liquid calcium supplement to add to the water and have been
doing that. Is it something you recommend?
<Not especially. Crabs are well able to feed on calcium-rich foods, so
unlike, say, pet reptiles, lack of calcium isn't a major threat. Still,
won't do any harm.>
What about an iodine supplement for the water? Would you suggest
adding that as well?
<I would. Does seem to help pet crustaceans of most kinds.>
I finally did find a filter I didn't mind - it is actually a turtle
<Looks well designed and adequate for your (crabs') demands, though
likely underpowered for pet turtles!>
It seems to do a good job; I just have to make sure I keep the water
level high enough so it is quiet enough. With what I built from
Plexiglas I made a small error on measurement for the height, due to
where the water level needs to be with the filter, so the water washes
away some of the sand on the top level, so I am going to purchase some
very thin Plexiglas to add to the bottom to raise it up slightly.
I am sure I will never stop thinking of new ways to come up with fixes
<Part of the fun.>
I just hope that this thing I made will help with the sand stink problem
now, since the sand is only a thin layer around the tank.
<Should do. You could also add a few borrowing snails like Melanoides if
you wanted (these are happy up to 50% seawater salinity) and
"bioturbate" the substrate very effectively, ensuring oxygen gets down
into as much as the top inch of sand, which minimises the risk of bad
smells (which come from anaerobic decay). Downside of course is that
they may become a pest in their own right. In a small vivarium, manual
removal is not big deal, but it's a personal thing whether to use these
fast-breeding snails. I like them, but many people don't.>
We'll see how it goes after a few weeks. At least cleaning will be
easier since all I have to do is empty the water, clean off the
Plexiglas thing, and clean the tank and put new sand. There won't
be those huge piles of stinky rotten sand like there was before!!!
It really was getting bad!!!! Anyway, I just wanted to update you
since I know it has been quite some time. I figure I would let you
know the crabbies are all still living!!! YAY! As far as
molts go, the male only molted once since the last time when he got his
big claw back. Mrs. Crabby hasn't molted for quite a while as far
as I know. And the two new mistresses....despite their size
difference...both molted on the same day!!!! It was quite
surprising. Hope all is well and I will keep you updated. If you
have any suggestions for me with anything I have said or any concerns
for what I have created in my tank, let me know. If I have any
questions, I know where to come!!!
<All sounds good to me. Thanks for writing. Cheers, Neale.>
Re: fiddlers - a few things RMF guesses
chatting here is better for folks than going to the bar
So, some good, yet odd news compared to what I've emailed lately....
Since my last email, none of the girls have had eggs. As of my
last email, one had them and once she got rid of them, that was it - no
more eggs. It is very odd. The male has been mainly hanging
out in his cave and the girls in the water area. Do the girls go
through some sort of cycle where they are able to carry eggs for a
certain amount of time and then that is over?
<Quite possibly. Declines in fertility are not uncommon among
wild-caught fish and invertebrates upon being kept in aquaria for some
months… perhaps related to diet; on the other hand, may be a routine
(seasonal?) thing or simply an occasional pause in breeding that happens
for no obvious (to us) reason.>
Although it would seem odd since all three were carrying at the same
time and now none are.
<Not necessarily a bad thing…>
Anyway, the good news is that FINALLY, my Mrs. Crabby was able to
molt!!! It had been since beginning of January that she molted the
first time and she hadn't since then because she was carrying eggs
almost constantly and now finally I saw a molted shell! I was so
happy for her. I swear she almost doubled in size.
<Good news indeed.>
She is very light in color and staying in the chest where she molted.
She was also acting quite odd and disoriented. I am keeping an eye
on her and just making sure I get food in there and that the others are
leaving her alone for the most part. She is quite the tough
gal...and she just seems to need to get used to her new long limbs.
The other crabbies are just hanging out; Mr. Crabby doing his wavy thing
all over the tank or hanging out in the cave...the other two girls are
basically just staying away and hiding, either under the bridge or in
the cave. I was just so thrilled though that Mrs. Crabby finally
molted!!! Although I am a bit confused at the lack of
mating....not that I can't say I'm not happy about this turn of
<"These things happen," as my father used to say. No need for alarm just
yet. Cheers, Neale.>
Re: fiddlers - a few things; beh., sys.
Me again J
I have some bad news...one of my crabbies is no longer with us.
We called her Ms. Escape Artist and, well, she finally escaped off this
Earth four days ago.
I always do a "count" in the morning and evening to make sure all four
crabbies are accounted for and the other day I was rushed in the morning
and in the evening, there were only three. I'll tell you what
happened, but it also leads me to a few questions for you.
Ms. Escape Artist was one of the two mistresses I purchased for Mr.
Crabbie. She was the larger of the two and typically spent her
time away from the others. She had tried to escape at least five
or six times that I can think of - by crawling up the cords of the
heater, when I was cleaning their tank she tried to crawl out the
temporary tank a few times (made it out once), crawling up the higher
log area when the tank top was off (made it out once)....so I was always
careful of how I arranged the tank heater and filter cords. I knew
she couldn't crawl up and out because of the lid. I knew she
couldn't crawl up and fall down and out because it was enclosed.
However, I knew if she fell into the enclosed area for any length of
time, obviously she could dry out, get stressed, etc. so I always kept
the cords a certain way. With my last cleaning, I took the entire
tank off the table and in doing so, must have shifted something. A
few days after the cleaning, I fed the crabbies, and three of them
popped out of the one ornament to get food. I found it odd ALL
three were in the one place together because they normally were in their
own areas. Anyway, that night when I did my "count", I counted all
three still in the one ornament?!?! And then could not find
"four". So I began to tear apart the whole aquarium, taking out
ornament by ornament trying to find "four". Finally the tank was
nearly empty and I realized "four" was not in the tank. My heart
sunk as I opened up the lid and looked down. Sure enough....there
she was...belly up in the bottom of the area. I reached in and
took her out and tried to get some of the "salt water" on her but to no
avail. She must have crawled up the cords the previous evening
because with the plastic container, had she done it during the day, we
would have heard her crawling around in there. Of course, I was
completely heartbroken. It has taken me this many days to email
you about the situation.
This all has led me to some questions about the death of crabs.
1. Obviously the other three knew something was going
on because they were all huddled together in the ornament furthest from
the back. Do crabs give off some "odor" or something when they
<Not that I am aware of. On the other hand, whatever caused one crab to
die may still be present, stressing the remainder, or the pollution
caused by a decaying crab could be unpleasant to them (though I hasten
to add crabs pretty quickly devour crab corpses in the wild). Or else,
what you see is pure coincidence. Crabs aren't especially intelligent
animals and social interactions between Fiddlers seem to be based around
body language, which both count against some deeper level of
communication between them.>
I know when my first crab died, the second died within a day or so and
when I had the group of crabs, they all huddled together and all died
within 24 hours of each other (those lost limbs besides). So do
they somehow know when one is sick or dead and stay away? (also as
soon as Ms. Escape Artist was removed, the other three came out of their
one area and resumed going separate ways).
2. Do crabs mourn one another? Ever since the
passing of the one crab.....the other crab I purchased with her has
basically stayed in one spot while the other two, Mr. and Mrs. Crabby,
have gone along and done their business as always. The little Baby
has sat on top of this little ornament towards the back where the other
crab usually was. Is there some bond between Mr. and Mrs....and
then between the two mistresses which were purchased together?
<Unlikely. Of course many animals do develop strong pair bonds, but
invariably these are where both male and female have to rear young
together, and they need to have a strong bond for that to be successful.
Only female Fiddlers carry the eggs after fertilisation, and even then,
only until the eggs are ready to hatch and the larvae released into the
sea, so there's no need for males and females to form pair bonds.>
The Mr. and Mrs. don’t seem to care a bit that one is missing; while
Baby is in the same spot every time I look in on them. Only if I
reach in will she move off her perch. She wasn’t like this
before...normally she hung out by the heater, or in the other ornaments,
etc. This is different behavior for her.
<Apart from Elephants, no animals other than humans seem to recognise
dead individuals as their own kind, and so mourning behaviour doesn't
seem to happen -- as far as we can tell.>
3. What are the odds Baby will die now that her
“partner” is gone? Is there anything I can do to help her with
what she is doing so she doesn’t just sit on her one spot?
<I would instead review the vivarium. It looks lovely, but double check
water quality, water temperature and salinity. If you can, check
humidity (you can get inexpensive stick-in humidity measurers for
amphibian tanks in some pet shops or online, the basic Exo Terra
Analogue Hygrometer for example is under $6 on Amazon). Fiddler crabs
are sensitive to dry air and cool air, so you want to keep the air
inside the vivarium warm (around 25 C would be ideal) and very humid. Do
also review diet including vitamin and calcium supplements (which I
think we've discussed before).>
4. Mr. Crabby didn’t usually mate with Baby, as he
mated with Mrs. Crabby and the other larger female most often; so I
assume, he will be back to mating with Mrs. Crabby again a lot.
Should I get another female? I am scared to introduce a single
strange female; however, maybe it would be better since if Baby is
mourning her “partner”, maybe they shouldn’t be bought in pairs?
<You could try getting two females or maybe two females and a male, put
them in a bucket, remove the existing crabs as well, move the rocks
about, then introduce all the crabs at the same time, so they all think
they're somewhere new. An extra male may give the existing male
something to divert his attention. To some degree, the more you have,
the easier they are to keep because it's hard for any male to hold a
Well, I know I am still mourning my little Escape Artist. I know
she wasn’t truly happy in the tank as she was always trying to be away
from the others and always trying to escape.....but it is still so
difficult as I was doing so well with them!!!
Mrs. Crabby is with eggs again of course.
They seem to love my Plexiglas creation. I’ve taken and attached a
picture for you. It has given them a lot of water, which they
love; but they also have the land area under the log if they want to be
on land. In reality, they didn’t actually lose a lot of land space
because before, half the tank was full of gravel/sand/etc. and then they
had the little land area on top....which is what they have now.
All they gained is a lot more water space and more ornaments to hide in
from each other J.
<Certainly an attractive looking environment!>
So, I guess let me know your thoughts on things. You’ve been so
much help to me you can’t even know!
<Would draw your attention to the recent (Volume 10 Number 3, May/Jun
2013) issue of 'Coral Magazine', which had quite a bit (6-8 page)
feature on keeping Fiddler crabs, and the next issue I believe the
article continues with behaviour and breeding. You can get back issues,
which may well be $10 well spent if you want some genuinely deep and
thorough information on these animals. I gave my copy away to a marine
aquarist friend so don't have it to hand or else I'd summarise it for
you, but anyway, do see here:
May also be available at your local marine aquarium retailer. Hope this
|RE: fiddlers - a few things
Thank you so much for the information. So, from what it sounds like, I
am attributing human traits to the crabs (a bad tendency with animal
<Possibly, but we all do. I've got a catfish called Claire who I openly talk
to and introduce to house guests… Basically, treating animals like humans is
fine, I think, provided that such affection isn't an alternative to the
actual species-specific care they need. Make a Facebook page for your dog if
you want to, but remember to take it for walks too, and let it socialise
with other dogs as often as possible. That's my angle, anyway.>
Overall, there haven't been any changes with the water salinity, humidity,
feedings, water temperature, etc. That is why I am worried about the
behavior of the Baby. It is highly unusual for her.
<Perhaps. Do also remember crabs go into a rather withdrawn mood before
moulting, which should happen every couple months.>
You mentioned elephants recognizing when one of their own has died, but I
have seen squirrels and dogs run out into the street to try to arouse a dead
mate (or pal). Not too long ago there was a video of the one dog
sitting by another dog who had been hit and killed. The dog sat for
hours trying arouse or pull the other dog out of the middle of the road.
I believe finally some people had to stop and pick up both dogs. I've
seen two squirrels playing, one get hit and the other go out into the middle
of the road to try to nudge its mate or pal back to life at the risk of its
<Ah yes, I shouldn't have been clearer. What Elephants do that seems unique
-- apart from humans -- is that they can recognise long-dead remains, even
bones, as of their own kind. It's one thing a mouse sniffing a recently dead
mouse, maybe logical if it's trying to figure out the cause of death.
There's an evolutionary advantage to that sort of curiosity. But what
Elephants do is pick up bones, move them around, guard them, and generally
exhibit a degree of "tenderness" or "emotion" that seems (to us) most
un-animalike. I had a university zoology professor who reckoned that
intelligence wasn't limited to humans and the great apes, but probably
applied to Sperm Whales and Elephants as well, both of which seem to exhibit
intensely strong social behaviours far beyond merely being smart like
dolphins or dogs. Do have a read:
There's quite a bit of scientific literature on Elephant behaviour. I do
remember watching one feeding at the Budapest zoo and he rolled the melons
under his foot very gently, and ate the pile of hay first. It looked very
much like he was saving his favourite food for last!>
I guess for those reasons it just seemed the behavior of the other three
seemed odd that they were all huddled into the one ornament and as soon as I
found the one and removed her....the others dissipated and went along with
their business. So for me it seemed like putting two and two together
would be that somehow they knew or could smell and were staying away.
I know they certainly develop an odor within 24-48 hours of being dead!!!!.
<Oh boy yes! I know it well from my marine zoology education. Snails are
almost as bad. Something about the decay inside a shell that makes a really
Thanks for the article. I found it online and downloaded the pages
relevant to the Fiddlers. You can be sure I will read it
<Hope of interest. Didn't know you could get the articles singly!>
In the meantime, I am going to go give some food to them to see if I can
<Maybe try upping the temperature a degree or two. If you can rig some
direct sunlight instead, that often works wonders, with animals just as much
Thanks for your help!
Salt-Marsh Environment 3/19/12
I recently found some Fiddler Crabs at the local pet store.
They were, of course, being kept in a freshwater tank with no way to get air. I
did not purchase any, but I did start doing research. I will be working at a
science center this summer, and I think that a Salt-Marsh Ecosystem display
would be really neat.
<Can be, and you do see such terrariums at many public aquaria, zoological
It would consist of approx. 70 gal. long tank with a fine sand substrate. Do you
think that four inches of sand would be good or more?
<Hmm… unless you're growing plants, would minimise the substrate. While the
crabs can dig burrows, they dig into mud, and plain sand doesn't "shore up"
adequately for that. So, if you wanted burrows for the crabs, better to use
plastic or ceramic equivalents (such as PVC tubes covered with sand) and
minimise the actual depth of sand to whatever is needed to hold the rocks in
place and to provide a realistic terrain.>
If so how many?
<Would keep a fair-sized group to minimise aggression, and ideally more females
than males. Anything upwards of 6 should work, but in a tank this size, and that
would leave space for Mudskippers. But if just the crabs, then easily a dozen or
Should the water be kept at more 1.000 or 1.015?
<Anything between 1.005 and 1.010 should be adequate.>
Is there a way to purchase the grasses and other plants that grow naturally in
the marsh not online?
<Yes, they can grow, but with some complications. Firstly, you'd need a
substrate with mud of some type at the bottom (a few inches of pond soil would
be fine) topped with an inch of sand for aesthetics. Secondly, grasses tend to
need strong lighting, I'd have thought at least 3 tubes the full length of the
tank, and probably 4 or more. Daylight, if possible, would be even better.>
What are some of the most common species of plant that would grow in the region?
<Many, many types. Aquarists generally have the impression there are few
brackish water plants, but that simply isn't true. Unfortunately, few are
traded, so you do need to do independent research here. The Aqualog brackish
water fishes book has a fair summary of salt marsh plants, but you'd be better
off reading something like Dynamic Aquaria if you can for a full listing of
species and their salinity preferences.>
What types of rock would be best? Limestone, Granite, Sandstone, Lava Rock?
Drift Wood is okay or not?
<Any and all, though the system might look better with a single type of rock as
that's what you'd see in the wild. Bogwood is also useful. A few nondescript
shells like oysters and mussels can add variety, perhaps heaped into a "drift"
like you'd see in the wild, or with the oyster shells cemented to rocks to form
The tank would have a small section of brackish water on either side. What foods
would be best to feed them?
<They're very omnivorous, so virtually anything edible. Algae wafers, frozen
krill for calcium, bloodworms, soft fruit...>
Would heat lamps be good for keeping the entire thing (open air) warm or should
a heater be used?
<Any, so long as the air doesn't get colder than, say, 20 C/68 F. I'd probably
go for the heat lamp if the water was shallow; also consider the under tank heat
Would an aerator be enough for the small ponds of brackish water?
<If necessary, yes.>
Thanks for all your help.
Enjoy life this week!
Fiddler Crabs, sys. mostly
My daughter brought home a fiddler crab from a school experiment.
I felt so bad for all of the creatures that were purchased for the
classroom (frogs, crabs, millipedes, etc).
<I would, too. Using live animals in schools is really not a
brilliant idea, and I fear that many teachers are just as ignorant of
animal care as the children in their care.>
There was a very high mortality rate.
<I'm surprised that this is legal, especially where vertebrate
animals like frogs are concerned.>
So rather than buy what were being passed as hermit crab habitats at
the local pet store, we bought a 10 gallon ZooMed terrarium.
<Sounds a good start. Fiddlers are amphibious animals and spend 90%
of the time on land feeding, but will need to go into heated, brackish
to marine water periodically.>
while at said local pet store I saw another fiddler crab in a
freshwater goldfish bowl.
Having remembered a post from your website I told them that they
weren't compatible. They said that you didn't know what you
were talking about because the "little guy was doing fine".
So I bought him as well.
We followed all the directions to the letter. The two (male and female)
were happy as...well clams. Now they don't seem as happy now as
they did before.
They stay in their burrow all the time.
<Likely the air is too cold or dry.>
They don't seem to be eating.
<How are you heating their vivarium? An under tank heating mat would
be a good start.>
I'm getting concerned. We currently have a freshwater bowl, a
brackish water bowl and the rest is aquarium sand mixed with hermit
<You don't really need the freshwater. What you do need is
enough brackish water for the crabs to cover themselves periodically,
so a couple of inches. Salinity needs to be about one-quarter that of
normal seawater, SG 1.005 at 25 C/77 F, or marine salt mix in water at
a concentration of about 9 grammes/litre or 1.2 oz/US gallon.>
I'm wondering if I've gone too far the other way and
they're not getting enough water.
<Does depend. You can keep Fiddlers in a half-filled aquarium with
the water filled and an aquarium heater installed, and then lots of
above-the-waterline stuff for them to climb about on. Warmth from the
water will heat the air and keep it humid. Alternatively, you can
create a vivarium, with just a pool of water, and use an under tank
heating mat to warm the land and air, and the humidity will rise from
the moisture in the land (typically sand or coconut fibre you spray
every day or two).>
The tank has a 30% humidity level -- which I see now is too low.
So perhaps I need to either mist or pour brackish water into the tank
It has a full screen top on it. I have an under tank heater that
I've attached to the back of the terrarium.
<Uh, no. The under tank bit is the clue! It goes under the tank, and
heat rises. Attached to the back pane of glass it'll do nothing at
all because the heat will rise away from the tank.>
I just don't want to make things worse for the poor little guys. I
was also thinking about partially covering the top with some Plexiglas
but not sure.
<The vivarium should have a balance between humidity and
ventilation. Put another way, you need some of the warmth to be kept in
by the hood, but you also need a gentle flow of air through the tank to
Please help me....and them. Robin
<Hope this helps, Neale.>
3 fish questions, Pantodon repro., Koi color change,
Fiddler crab sys. stkg. 1/16/12
I got a butterfly fish (freshwater) the other day . recently I noticed
a group of bubbles on a bamboo leaf ,the next day there were tons in my
tank (bamboo plants and surface) what is going on?
<Pantodon... is a bubble nest builder, spawner...>
should I get him/her a mate?
<Mmm, up to you. Do see the brief notes here re sexing,
reproduction, rearing the young. And elsewhere re raising food/s:
In my outdoor pond (12ft wide 6ft deep)
I had a 2 foot Koi in my pond (I live in MD).he started out orange and
white but over 3-4 years he changed to all white to orangish pink to
sort of transparent to white with a orangish pink head is this
<Happens... due to genetics, foods/feeding and water quality mostly.
Best to not allow such stock to reproduce>
And last I would like to set up a ten gallon vivarium
with 1-2 fiddler crabs . is it okay to put a small fish in the water
Like a Betta or something?
<Not generally, no... water quality too variable, crabs too
predaceous... Bob Fenner>
crab water quality, salt type/s
I recently set up what I thought was a brackish tank for one
red clawed crab and a few guppies. I got all animals from a
LFS that was going out of business. They said they used aquarium salt
and iodine supplement.
After doing some more research I see you site says aquarium salt will
not do long term.
<Ideally not. Mixed with Epsom salt and baking soda it would be
okay, but the ideal would be to use marine aquarium salt by
I have a partial package of instant ocean marine mix but do not know
what the measurements for adding it to the tank are. It only says to
use full package in 5 gallons water.
<For a low-end brackish aquarium, something around 9 grammes/litre
should be ample. There's about 6 grammes per teaspoon, so you
shouldn't have much difficulty estimating this amount: 1.5
teaspoons per litre!>
What would the correct measurement for adding that? Also, is that what
I should order since I have to order salt for correct brackish
<You can use your tonic salt until it's used up, but after that,
buy the marine stuff.>
It will be a few weeks before anything gets here. I saw on another
question you told the person they could "add 1 teaspoon baking
soda (sodium bicarbonate) and 1 tablespoon Epsom salt (magnesium
sulfate) per 10 liters alongside the aquarium salt.
<Yes, adding those amounts to baking soda and Epsom salt should be
Ignore the salt amount quoted there, because that recipe is for
freshwater, not brackish water, conditions. In other words, per 10
litres, something like 1 teaspoon of baking soda, 1 tablespoon of Epsom
salt, and 15 teaspoons of tonic salt should provide a specific gravity
around 1.005 while also producing hard, alkaline chemistry.>
These will provide some of the minerals crustaceans need for their
<Correct; do see above.>
Also, add the iodine, either in the water, or through foods rich in
iodine". Should I do that until I get the correct stuff in?
<Alongside the others, at 50% the dosage on the marine aquarium
How long can I use that for?
Will all of that be safe for the guppies?
<Yes, but it's questionable whether crabs and guppies will get
Do I simply add that when I do water changes and let it dissolve before
putting into tank?
Also, the iodine supplement I have is very concentrated and I am not
sure what the correct dosage is. The directions are one teaspoon (one
capful) per 50 gallons each day. My tank is only a 20gallon.
<Sounds like a couple drops should be ample.>
Thank you for your replies.
Molting or dead? 9/7/11
Hey thanks so much for the speedy response to my brackish tank
<Glad to help.>
I have a new dilemma. I was in the process of changing my
freshwater tank slowly to brackish, following the
instructions that someone on your site gave me about slow water
changes, when my fiddler crab decided to molt. At
least I think he did. He is down in the water upside-down and not
<Not a good sign.>
He was like that when I got home from work and has remained that way
for at least an hour. Two of his legs are gone and part of his large
claw is missing. He's almost all white and there is a white film on
his belly and big claw. The rest of him looks pretty solid. I read that
this could be his exoskeleton and he might be hiding somewhere but is
there any way I can tell for sure?
<The exoskeleton looks like a "ghost" of the original
crab, and is obviously hollow and empty. When you pick it up, it weighs
hardly anything at all.>
Was the water chemistry just too hard on him and he died mid molt?
<Possibly, but if your Fiddler Crab has simply died, there are a
host of reasons for this, from aggression between males (rare, but
happens with some species) through to stress from being kept in
freshwater for too long.>
He looks so sad just laying there.
<I bet. Good luck, Neale.>
Molting or dead?
Hey thanks so much for the speedy response to my brackish tank
<Glad to help.>
I have a new dilemma. I was in the process of changing my freshwater
tank slowly to brackish, following the instructions that someone on
your site gave me about slow water changes, when my fiddler crab
decided to molt. At least I think he did. He is down in the water
upside-down and not moving.
<Not a good sign.>
He was like that when I got home from work and has remained that way
for at least an hour. Two of his legs are gone and part of his large
claw is missing. He's almost all white and there is a white film on
his belly and big claw. The rest of him looks pretty solid. I read that
this could be his exoskeleton and he might be hiding somewhere but is
there any way I can tell for sure?
<The exoskeleton looks like a "ghost" of the original
crab, and is obviously hollow and empty. When you pick it up, it weighs
hardly anything at all.>
Was the water chemistry just too hard on him and he died mid molt?
<Possibly, but if your Fiddler Crab has simply died, there are a
host of reasons for this, from aggression between males (rare, but
happens with some species) through to stress from being kept in
freshwater for too long.>
He looks so sad just laying there.
<I bet. Good luck, Neale.>
Fiddler Crab question
I save a fiddler crab at work, the bigger one took all of but one of
his legs off.
<That is what males will do. These are amphibious, mostly
terrestrial brackish water animals. They generally don't do well in
small aquaria, and if the water is freshwater rather than brackish or
marine, they tend not to live very long anyway.>
he has the feeder claw and that's it. I have him in a small bowl at
the moment with gravel in it. Can you give me some suggestion to help
"Little Man"(his name) out?
<Some people have hand-fed crabs every couple of days until they
grow their limbs back, but this is pretty labour intensive and will
take some weeks if not months. Euthanising the animal may be more
appropriate depending on the amount of effort you want to make.>
I have tried to research this situation and have not come up with any
<Almost all problems with Fiddler Crabs come down to lack of
research, e.g., keeping them in freshwater rather than brackish/marine,
or keeping more than one male in a small habitat, or not keeping enough
females to go around (at least two, and ideally four per male), or
keeping them in an aquarium rather than a mostly dry land vivarium.
It's a shame that this is the case, because kept properly these are
hardy and amusing animals.>
<Hope this helps, Neale.>
Hey, I have some questions on fiddler crabs and red
claw crabs. 7/22/11
<... Okay... have you searched, read on WWM re already? Bob
re: FW, BR crabs, rdg. 7/23/11
I have but I don't think my questions are on here. I'm
wondering mostly how well red claw crabs and fiddler crabs do
<Not at all... is this a brackish system?>
and how many I could have in a 20 gallon long? I'm also wondering
if red claws are more shy than fiddlers bc I see my fiddler alot <No
such word> more.
<Go back, read on WWM re these species:
and the linked crab files above. Bob Fenner
Help?, Crabs and Goldfish 3/2/11
So I'm looking at setting up a fish tank, and I was wondering if it
was ok to keep freshwater fiddler crabs and goldfish together. Also any
advice on this would be wonderful.
Thanks, Steven Bauer
<They are not compatible, see here for more
Re: Help?, Crabs and Goldfish 3/3/11
Thank you so much. I would have hated to set my tank up and have one or
the other die.
Crab Questions, Fiddler longevity, beh. f'
Hello, I am sending this email as a reply to facilitate "the whole
story" being together in your wonderful archives, but our last
correspondence about this Fiddler crab was a couple
years and several months ago.
<Ah, I see>
I was down to a male and a female left in October 2008, and around
December 2008 the male died after sitting in a little tree for two
days. Due to some bad personal circumstances, I did not buy more
Fiddler crabs to go with the female (I had been a bit discouraged /
surprised by the male pulling the legs of the other female who was
carrying his eggs earlier too, despite having access to proteinaceous
<Yes, crabs can be unpredictable, and not entirely easy to keep
So this last female Fiddler has been living with me since the summer of
2008, and she has been active and molting well and so on until December
24, 2010 when she molted out in the open (versus her standard area in
the coconut house) and she did not eat any of the molt. She looked
larger after the molt and her appendages and color all looked great.
She will not eat since then (makes no poop, so it is certain) and just
wants to sit in the tree.
She responds as far as putting up her claws and legs and hiding behind
the tree. Every day since then I have expected to find that she has
passed on, but she is still here and I was floored to find another molt
out in the open yesterday (she still has all of her appendages and
normal color, but I can't tell her exact size because she is
hiding). We had discussed earlier that Instant Ocean in her brackish
water should be supplying the iodine she needs, and if it is "just
her time" she is certainly going much slower than the other
<It is odd. Crabs generally don't moult anymore once they reach
adult size. So old specimens tend to have shells encrusted with sealife
(sponges, barnacles, etc). So if she's moulting, she's probably
not life expired. Do check humidity and air temperature is good -- the
tank should be warm and humid, feel free to spray with luke warm water.
If she seems healthy enough, then leave her alone. Usually there
isn't much you can do with crabs -- they're either healthy or
dead. If yours has been around for a couple years, it sounds like
you're doing all the basic things right. Stick with it, and see
what happens. Possibly offer a different type of food, but don't
fuss overly much.>
I would appreciate any thoughts or comments about this situation.
Re: <Fiddler> Crab Questions /Neale
Just wanted to say that the Fiddler crab died at the end of March after
not eating since at least Christmas (she didn't make any poop
either, so was definitely not eating). I read about acclimating ghost
shrimp to her brackish water and added some and it was just the thing
to get her moving about the tank., I was amazed at the difference. She
tried to scissor them at times, and one time she was even letting them
clean a tiny bit of algae that had grown on her back. How she was able
to do all this on an empty stomach, I will never understand. The night
before she died she was riding around on a floating plant trying to
pinch the shrimp that were eating the food that she wouldn't eat. I
had her for at least two years and eight months. I have since raised
the water level in the tank and am enjoying the ghost shrimp.
<Glad that your Ghost Shrimps are happy. Unfortunately your
experiences with the Fiddler Crab are not uncommon, and virtually
nobody keeps them properly, which is why so few of them last for more
than a few months in captivity. They do need brackish to marine water
for bathing, but are otherwise terrestrial, and outside of a vivarium,
are very difficult to keep healthy. Shame really, because they are
quite amusing animals. That your specimen lived almost three years is
remarkable, and I hope that encourages you to learn more about these
and other crustaceans, and in time, perhaps try again at keeping them
in a more carefully created environment tailored to their needs.
re: Crab Questions
Well, I did have a proper Fiddler environment, with brackish water, and
have lovely videos and photos of tunnel digging in the sand, etc. I
even had Fiddler zoea though they didn't make it past five days on
phytoplankton and zooplankton. That was kind of my point, that people
shouldn't buy them and drop them into deep freshwater tanks.
<Uhh, we're in agreement... w/ the purchase of any life comes
the onus (if you will) of pre-investigation/knowledge and provision of
adequate care. If it will serve to prompt folks, "the more you
know, the further you'll appreciate, enjoy"...>
Besides being cruel, it is a waste of money - they should get a crab
ornament instead that won't disintegrate.
<Thank you Rose. Bob Fenner
Hello, I was wondering if ghost shrimp, Amano (algae eating)
shrimp and fiddler crabs
would be compatible with each other.
I know fiddler crabs require brackish water, but what salinity can the
shrimp tolerate? If they get along, what SG would be best for all
species? They would be in a 30 gallon tank. I would provide sufficient
habitat/hiding spots for all species including water plants for the
shrimp and adequate land for the fiddler crabs. Thanks.
<Funnily enough Amano shrimps develop in the sea, but the adults
mostly live in freshwater. But they will tolerate slightly brackish
conditions just fine, certainly SG 1.003 to SG 1.005 at 25 C/77 F, and
little higher. In fact most shrimps tolerate slightly brackish
conditions, and I have some Cherry Shrimps in a tank at 1.002 at 25 C
alongside some Limia nigrofasciata. But Uca species may need more
saline conditions depending on the species. Plus, Uca are
opportunistic, and while their diet is primarily algae and organic
detritus sifted from mud, they may catch shrimps given the chance. So
by all means try it out and see what happens, but don't invest a
huge amount of money in this just in case it doesn't work. I'd
try out the brackish water Palaeomonetes sold as live food -- at least
here in England -- before investing in more ornamental shrimp species.
hi I am, Godffrey Nazaire conducting a thesis entitle
"Macroinvertebrate diversity in mangrove swamp of Barrio Ilang,
Davao City" would like to ask from you if you can help me
identifying this species of fiddler crab attached here.
hoping for your kind consideration
hoping for your positive response
University of Southeastern Philippines
<Hello Godffrey. May I share some tips with you about asking help
from academics. First, start by checking that they work in your field.
My own PhD is in geology, and while I help out at WetWebMedia with
regard to freshwater and brackish water fishkeeping, I am not a fiddler
crab systematist. Next, be sure to start your message with a personal,
relevant greeting. Asking someone to identify an organism -- in other
words, asking them to spend their time doing your work -- is a
significant favour. Many academics are happy to help, and thoroughly
enjoying talking with other people interested in their aspect of
science. But most academics will expect a personalised message. Perhaps
mention how much you enjoyed reading one of their papers, or that you
are particularly interested in some bit of science they are working on.
If another academic mentioned their name, then say so. Make it clear
that you know them and their science, and didn't just find their
name on Google. Finally, don't send the same message to a bunch of
people at the same time. Each message should be unique. By looking at
the "To:" field on your message, I can see you sent it to at
least five different people. That doesn't make me, the reader, feel
special. Here at WetWebMedia we are all volunteers, and we each spend
anything up to an hour a day answering e-mails from people with sick
fish, plants and invertebrates. I'm sure the other academics you
wrote to also have pressures on their time. It is therefore very
important you make the recipient of your message *want* to reply,
rather than make them annoyed. I'm taking the time writing this all
out precisely because I was once a BSc student and a PhD student, and I
certainly want you to enjoy your scientific education and get the most
from your interactions with other scientists. So I hope you take this
reply for what it is, advice that should make your communications with
other scientists much more successful.
One last thing, at WWM we do specifically ask people keep attachments
down to 500 KB or less (yours was over 6 MB). Big messages clog up our
limited e-mail Inbox capacity, meaning other people -- often with
emergencies -- have their messages bounced back. And I'm sure
I'm not the only person who does not like to see Word .doc
attachments in unsolicited e-mails. These can contain viruses, and
often recipients prefer not to take the risk of opening them. If you
need to send an image, send a JPEG, preferably reduced in size. Good
luck and Merry Christmas, Neale.>
Crab Identification: Fiddler Crab
<Ah, bonjour Marie, Lynn here today!>
I received yesterday 2 little red crabs from the Philippines and
I'm not sure what they are because of the eyes. I think they
may be fiddler crabs...
<Youre right. The overall shape/length of the stalked eyes and
sharply pointed carapace seem to be fairly common within the
semi-terrestrial fiddlers in the genus Uca, family Ocypodidae.
The closest I can find is a photo of something alleged to be Uca
arcuata (see this link:
Unfortunately, I cant confirm the ID. Either the color/pattern
varies quite a bit (as shown at the above link) or theyre
different species entirely. Apparently, in the Philippines, these
are mainly mangrove/shallow water/intertidal crabs that make
their burrows in the mud and sand. Interestingly enough, Ive seen
a similar species being offered for sale on the internet, listed
as a Red Burrowing crab in the genus Uca. >
..even if they don't have the oversize claw... maybe
<Yes, my thought as well.>
I sent you a picture, maybe you can help me with this
<I sure wish I could give you a solid ID to species level, but
there are just too many possibilities and not enough available
information on the net and within my research books.>
I don't want to give bad information to my customers.
<Good for you! I wish all merchants were this conscientious!
Unfortunately, I have to add that these little crabs should not
be kept in a fully submerged marine system. Theyd do much better
in an environment more closely resembling theyre natural habitat
(mixed land/water). For more information on this group of crabs,
please enter the terms (Uca or fiddler) into our Google search
engine (http://www.wetwebmedia.com/Googlesearch.htm). Ive seen
several posts regarding solid red fiddler crabs with reports of
them being very reclusive. Apparently, once added, they tend to
burrow/hide and not come out much. In Barnes Invertebrate Zoology
(sixth edition, pg. 717), it states that tropical species of this
genus tend to be active only during diurnal low tides. Thats not
a whole lot, even in the wild! Also, theyre still crabs and
basically opportunistic, so hobbyists will need to keep these
well fed to discourage picking/killing of desirable
<It was a pleasure, Marie.>
<Take care, LynnZ>
Fiddler crabs in sea water... Not 11/08/07
Hi there, I am trying to set up a fiddler crab tank for a high school
research department. I've seen a lot of references to the brackish
water these crabs need - <And land... most are only part-time
aquatic, if then... live in/on mud and sand> but the crabs we have
were taken at the beach. Should they be in pure seawater? <No...
land/sand... with some water to moisten themselves> Currently the
water we are using is from the same beach we found the crabs, but
I'm not sure if this is an optimal condition. Any information you
can provide would be greatly appreciated. Thank You!! Andrea Beatty
<Andrea... "Woman of the sea"... fitting name, eh? Bob
|Answer to a mystery query (FW crab) 8/26/05 Bob:
<Actually, Sabrina with you, today> In answer to
Sabrina's question about the "red crab" on http://www.wetwebmedia.com/swcrabidfaq3.htm
from 8/13/05, I believe I have the answer. <My
question?? Oh - OH! I see. Yes,
that was in reference to the surrounding entries ("Mystery
Crab") that I was helping Charlotte with.> I too bought
what the LFS was calling a "fire crab" (or so it sounded
with his slightly different accent from mine) for my nano. I tried
Googling this and found nothing. Mystified, I posted a pic of him
on reefcentral.com <I would love to see this image, if you can
grab me a link. If it IS an Uca/fiddler, I might be able
to get it closer to a species, for yah. Not necessarily
likely, but there are some great references on the web.> and
still everyone was baffled. It was when I went to a different LFS
that I realized what it is I and others are buying: A
female fiddler crab (my LFS who I thought was saying "fire
crab" was actually saying "fiddler crab" but
pronouncing it "FIDE-ler" and I misunderstood
him). Some LFS call them red crabs. Again:
orange, 1", walks sideways, black eyestalks, burrows in the
sand. <Does indeed sound like a fiddler/Uca sp., as far as
burrowing goes.> Mine has proven to be totally reef safe, hiding
about 99.9% of her life. I've seen her for maybe a total of 60
seconds in 3 months! The females do not have the typical fiddler
chelipeded and so look like something else. <Correct/agreed.>
The problem with this is that fiddlers are supposed to be given a
land/water environment, as they live in muddy mangrove patches and
near the shoreline. Unfortunately, a few seem to find their way
into the reef trade, and unwitting people like me and Sabrina wind
up with them. <Mm, again, 'twasn't
me.... "I just work here"
<grin>. Though I do have a couple
fiddlers.... but mine are in a large sandy terrarium
with a 2g saltwater swimmin' hole. They seem to be
doing quite well.> I'm sure she'd be happier in a
terrarium, but she does just fine it seems in my nano reef. <If
possible, you might consider setting up a land crab
system. You wouldn't believe how much fun they
are.> Hope this helps! <Thank you very much for
this! And again, I'd love to see an image of your
crab, if possible.> Alex
<Wishing you and your firely FIDEler
Fiddler Crabs I have a 55 g. marine aquarium with 45 lbs. LR.
I was recently given a VERY surprise present of a fiddler crab.
I've never seen one of these mentioned in any marine article.
<On our site: http://wetwebmedia.com/swcrabs.htm> What do they
eat? <Meaty bits of this and that> Will they harm my fish
(I am planning on a tank of blennies, gobies and other small fish) or
invertebrates (snails, an emerald crab, and fan worms)? <Slow,
sedentary to sessile invertebrates may be in trouble if your crab gets
hungry...> And how will I keep this guy happy? <Need to
have a place to get out, dry a bit... and cover to hide in, reharden
their exoskeleton during molting events. Bob Fenner> Thank you very
much for your time. Mike Rathwell
Fiddler Crabs? Hi. Thanks for all your previous help in the
past, both directly and through the creation of this site.
<You're welcome> My problem is this. I have a 35 gal tank
that I added 10 Trochus and 10 Astrea snails to about a month and a
half ago. Since then they have slowly died off to the point of about
six. I find many upside-down on the sand bed, and, up until now, I had
thought they had fallen off the Live Rock. However, I had failed to
realize that I had been given a "gift" of a Fiddler Crab
about two weeks prior to the addition of the snails. <The
"Trojan" gift crab...> At least that's what it was
called, and it looks like one (has the eye stalks, but doesn't have
the one, large claw--I'm assuming this is because its female. But
the Bad News Bears and Walter Matthau taught us what happens when one
assumes). <Well put> After the addition of the Fiddler, it
disappeared for months and I believed it to be dead due to lack of a
place to dry out. However, a few nights ago I found it out and crawling
around the rocks. My questions are these: Is this crab causing the
demise of my snails? <Maybe... are their bodies missing?>
Will it hamper my plans to add more invertebrates (mushrooms, leather
corals, star polyps, feather dusters, shrimp)? <Maybe... I would
pull it> If it is...then how do I get rid of it because I
haven't seen it except for that one night? Please excuse the long
email, and thanks very much. Michael Rathwell BTW Kingsley from
Aquarium Arts in Phoenix says hello. <Ah, say hello back for me
please. I would "bite the proverbial bullet" and drain, take
out the rock... and remove the crab at this point. Luckily a thirty
five gallon is not "that big". Please see here:
http://www.wetwebmedia.com/movingaq.htm re input on "moving"
aquariums, about the same list of steps, tools, materials as you'll
be doing. Bob Fenner>
Re: Fiddler Crabs? Thank you again. The snails did have their
bodies removed, but could this have also been from decomposition?
<Not that quick... a few days...> In response to your moving
idea, could a trap not be rigged up with a little bit of bait?
<Yes... a few types described on our principal site:
WetWebMedia.com> I have seen these mentioned on various internet
sites for the removal of pesky bristleworms, violent Mithrax crabs, and
other things. Would this sort of thing work for Fiddlers?
<Possibly> Seeing as how the residents of my soon-to-be mini-reef
are only 2 red Firefish, 1 smith's blenny, 1 featherduster, and 6
(numbers slowly declining) snails the moving shouldn't be a
problem, but I would rather not mess with restarting a tank (thoughts
of re-cycling and ammonia spikes sicken me, <Shouldn't have to
be recycled... just put back what was in there... including much of the
"old" water> especially when only 1 week away from putting
in the first corals). And to think...all of this work for a $4 crab!
Thank you for your advice and help. <Be chatting. Bob Fenner>