FAQs about Horseshoe Crabs,
Related FAQs: Horseshoe Crabs 1, Horseshoe Crabs 2, & FAQs on: Horseshoe Crab ID, Horseshoe Crab Behavior, Horseshoe Crab Compatibility, Horseshoe Crab Selection, Horseshoe Crab Feeding, Horseshoe Crab Disease, Horseshoe Crab Reproduction, & Crustaceans 1,
Micro-Crustaceans, Amphipods, Copepods, Mysids, Hermit
Shrimps, Banded Coral
Related Articles: Horseshoe Crabs: Latter Day Trilobites for
Some Systems & Crustaceans,
Micro-Crustaceans, Amphipods, Copepods, Mysids,
Banded Shrimp, Cleaner
Shrimp, P. holthuisi
Crabs, Squat Lobsters, Crabs, Arthropods,
Pycnogonids (Sea Spiders),
Systems of size... lots of soft sand... Likely
Building horseshoe crab tanks
I can't seem to find consolidated information on ideal horseshoe crab
tanks, just random spattering of information. What are ideal tanks for
horseshoe crabs? Will you critique the tank I would like to build?
I would like to build a tank that is 4x4 wide and long, and 2.5 ft tall,
made from non-porous cement. I'd like to line the bottom with a fine
sand substrate, and keep two horseshoe crabs in it with no other fish. I
plan to culture black worms and phytoplankton and feed them to the
crabs, and feed them snails as well. Is this an ideal diet or is there a
better way to feed them?
<Issa, that tank is definitely sufficient if you are only doing the
The fine sand will do wonders for the crabs. The crabs will sift through
the sand for food, but you do need to feed occasionally. The foods you
listed will work, but I would as some other meaty food to the diet as
Read on WetWeb re Horseshoe Crabs. Let us know if you have any further
questions. Cheers, Gabe.>
horseshoe crab, fdg., sys. gen.
I have been reading and researching your site on horse shoe crabs and
had a few things i wanted to discus with you. I have a little horse shoe
<The eastern seaboard species I'll assume>
in a 10gal salt water tank. he was about 2 inch's when i
got him, and now he is about 3 to 3 and a half. I have had him in the
tank for about a year at this point and he has not
starved to death. My salinity is between 1.024 and 1.025, ammonia and
nitrites are both at 0 or close to, my nitrates are kinda hi, but they
have always been high in my tank and despite anything i do i cannot get
it to come back down.
<Not so important w/ these relic species>
So far the only adverse affects to the high nitrates is a bit more red
hair algae than i would like (the snails keep in under control for the
most part) and my plant seems to like it as well (not sure what kind,
obviously saltwater plant, its kind of like a vine and it raises
little stocks that disk shaped "leafs" grow on).
There is a very healthy bristle worm population in the tank as well as
he seems to enjoy algae wafers made for Plecos and other such fish as
well as high protein wafers made for catfish and other bottom feeders.
He does seem to come out and eat with everything else in the tank and
chasses around bits of flake food but his favorite seems to be Hikari
Multi-Vitamin Enriched Brine shrimp. As for the trace elements in the
tank, i use Kent Marine Nano Reef two part supplement. It is recommended
for use every day, but i don't use it that way, i add that about one a
week, sometimes twice if I'm feeling spunky. Tank mates include
a mis-bar clown fish, a blue-green Chromis, peppermint shrimp, two
Astrea snails, two dwarf blue legged hermit crabs and a group of about 9
Zoas. There was at one time a mini brittle star that came in
with the Zoas, but i have not seen hide nor hair of that little guy in
over 7 months so i think he died and got ate, or just got ate. There was
a narsis snail and another Astrea snail, but the hermits wanted bigger
shells and they didn't like any of the upgrades that i provided for
There is about 6 to 7 pounds of live rock, and about 20 pounds of live
sand to make a sand bed of about 3 inches deep. The sand is larger
grain, not fine grain, but he really does not seem to mind. I really
love this little guy, he is awesome and by far the best purchase i have
made. Hours of entertainment watching him walk around the sand eating,
and swimming (not very well) upside down around the tank. And yes i know
how big they get, i have already located tanks that he can be
transferred to as he grows, including a fine grain, 6 inch deep sand bed
in a 180gal tank with plenty of Spionid worms for him to break up and
eat. I guess what i want to know is is there anything else i need to be
doing for this little guy?
<Doesn't appear to be; no>
As i have stated he has had no problems so far, but i want to keep him
this way. I have not found anything on your site with anything i really
need to change so I'm just double checking that i have not over looked
anything. its hard to know what your looking for when there is no
problem to solve. thank you for your time and for your help! i greatly
<Well, the other life, fishes and invertebrates would likely appreciate
lower nitrate... not easily done in the size/type setting w/ the
horseshoe... All will appreciated the larger habitat. Bob Fenner>
Re: horseshoe crab 2/6/13
Thank you for the quick reply! any quick tips for lowering nitrates in a
small tank other than moving them to a big tank? i would like everything
to be as happy in the tank as can be.
and the linked files above. The mechanisms, techniques of nitrate
control are the same regardless of size of the system. BobF>
Re: horseshoe crab 2/6/13
thank you very much!
<Ah, welcome. B>
Horseshoe Crab... sys., sel.
I have spent a lot of time on your website and will not buy anything
for my tank anymore without looking to see what you guys have to say
about it first. I've spent a lot of time the last few days looking
over all the info on Horseshoe crabs that you have, all the questions
seem to be people who bought them and are now trying to figure out what
to do with them, so thus I have not found all the info I am looking
for. I think the horseshoe crab is an amazing animal and am very
interested in setting up a tank for one. I was thinking to use a frag
tank style tank, something at least 4 feet long and at least 2 feet
wide, but only about 16 inches deep or so and setting up the whole
thing as a sand bed for the horseshoe. I would set it up so it shared
water with my reef tank
<... which is coldwater?>
so I could take advantage of the good water quality and filtration and
chiller that I have on that, and add more total water volume to my
system. The drawback of this is that I keep that system @ 76
<This won't work>
I see that the commonly available Atlantic species of horseshoe prefer
colder water than that, are the indo-pacific horseshoes better for
<IF you could secure one of these it might work>
and if so are they ever available and how do i tell the difference
between the species.
<Have never seen offered in the trade. ID info. you can find on the
Also if I can find one that can handle my temperatures how deep of a
sand bed should I set up.
<Four inches or so will likely do for the size of the specimen/s
you'll be able to keep here>
And is there any other advice you would have for setting up a tank
dedicated to a horseshoe?
<All I'm sure of is posted on WWM>
Lastly if this ends up happening, what quarantine recommendations do
you have for horseshoes,
<Mmm, a couple weeks isolation from other systems. Do track
metabolite accumulation in their quarantine system>
I am slightly paranoid about quarantine and have separate quarantine
tanks for both my fish and my corals, nothing goes in without being in
quarantine for a while.
<Welcome. Please do relate your experiences if you go forward w/
this project. Bob Fenner>
Atlantic Horseshoe Crab/Feeding/Systems 4/19/10
I have recently bought a Atlantic Horseshoe Crab and I am not sure how
often to feed him. I have 4 foot tank which is 350 lt.
In my tank I have clown fish, damsels, Chromis and 2 Chocolate Chip
<<This animal can't live here with these fishes... is NOT
My star fish eat white bait and the other day I put half of one in the
tank for the star fish and the crab eat it instead is it ok for the
crab to eat that.
<Yes, will eat most anything.>
Please let me know how often to feed him I don't want to starve him
but I also don't want to over feed him.
<This species is principally a sand-sifting filter feeder, though
there are other horseshoe crabs that are more predatory.
Most Horseshoe crabs are short lived due to lack of nutrients,
inappropriate systems. Do read FAQ's here.
<You're welcome. James (Salty Dog)>
Horseshoe crab arriving today, sys. (RMF, thoughts on
releasing Limulus into the wild? I'm against...)<<Am totally
opposed. RMF>> 11/17/09
I read with interest your FAQ section on Horseshoe crabs.
<Fascinating animals indeed.>
Unfortunately, I did so after ordering a 2-3" crab yesterday from
a website that said they are easy to raise and will do well in reef
<Good heavens no!>
I have a 125-gallon reef tank and a 55-gallon FOWLR tank.
<Not a good home for this chap.>
However, after reading your FAQ's, it is clear this new arrival
will not be happy in either place due to the water temp, among other
things. I want to give him the best shot at survival until I can figure
out what to do with him long term.
I have a 100-gallon Rubbermaid tub, 80lbs of Caribbean Live sand still
in the bags, plenty of "seasoned" salt water and cured live
rock, powerheads, etc. I will use whichever of these things I need to
for this crab and will purchase whatever else you think I need for the
next year, short of a new aquarium.
<Actually, maintaining Limulus under lab conditions isn't
especially difficult, and if you Google "Limulus polyphemus"
(the Latin name) as well as Horseshoe Crab alongside
"maintenance" and/or "aquarium" you'll find
there are fairly reliable protocols for keeping these creatures for
extended periods. While not precisely white mice, they are much used
lab animals, particularly for medical research. See for example,
In short, they're kept reasonably cool, room temperature in an
unheated room usually fine, and maintained in a clean, filtered
aquarium. Feeding is done separately, with the animal turned upside
down, food (chunks of fish, seafood, etc.) placed in its
"claws", and then the animal replaced in a tub of seawater.
It's left to feed for about an hour or until its defecated, and
then returned to the maintenance tank. Repeat every couple of days. In
the wild these animals hunt for small organisms within the sand bed,
but this really isn't viable in captivity.>
Please let me know the best way to set up these things to make a
suitable environment for him until he outgrows the 100 gallon
Rubbermaid (by the way, how will I know when he has outgrown it?).
Also, can I release him into the Long Island Sound once he grows and if
so, what size should he be before release?
<I'm not wild about releasing captive animals into the wild. For
one thing, at any number of points along the chain of handling it can
be exposed to parasites, bacteria and viruses that don't exist in
Long Island Sound.
There's also the issue that you may not even have Limulus
polyphemus, with Asian sources certainly sending out Carcinoscorpius to
pet shops in Europe, and therefore possibly elsewhere. Obviously
releasing non-native species is a bad thing. Since these animals do
reasonably well in public aquaria, you might send a couple emails out
to such places, to see if they can home your beastie. Alternatively,
humanely destroy the animal (again, info on this will be in the
scientific, if not hobbyist, literature).>
Lastly, would it be okay to purchase minced clams (like they use for
clam sauce) and chop them even finer for him?
<A variety of seafoods is best, since by themselves seafood items
tend to be lacking in one or other regard. Unshelled shrimps have
calcium but too much thiaminase, shelled cockles are low in thiaminase
but not enough calcium, and so on. The more variety, the less chance of
problems. Lab specimens take standard fish pellets readily enough, and
while there's debate about their use as a staple, as an occasional
vitamin top-up they may have their place. Alternatively, your usual
marine vitamin supplement could be used.>
Thank you for any advice you may offer.
<Hope this helps. Cheers, Neale.>
Re: Horseshoe crab arriving today, more re sys.
Thank you for your prompt response.
I will feed him/her as you propose.
I will set up the Rubbermaid home for him/her for now. According to the
seller, this is an Atlantic Limulus.
<Good to know. Telling the species apart isn't difficult, and a
cursory review of the literature should help if you're
I have an extra submerged pump/filter setup from a small koi pond which
I can use.
Should I leave the bioballs in there or just use the sponge filter?
<Probably won't make much difference either way. These
aren't "delicate" animals provided they aren't
starving or overheated (which are the prime sources of mortality in
Will the crab be okay with the water movement that comes from the top
outlet (used to be a fountain) of the pump/filter setup?
<These animals are used to very strong water currents, but that does
assume they're able to "dig in" a bit. I'd see how
you go. In aquaria they often get pushed onto their backs, in which
case you'll need to right them.>
Should I fill the tub to the maximum level? (100gal)
<More water the better of course, but 100 gallons for a 3-inch
specimen might be overkill.>
The only room I can put the tub in is heated. I will put a thermometer
in the water. What is my target water temp? Should I do periodic water
<Wouldn't worry too much. Unless the water temperature is above
20 degrees C, these animals aren't stressed. Do read that article I
linked for you; it contains details on the established
Lastly, should I not bother opening the two 40lb bags of Live Sand and
just leave the tank with not sand?
<In labs sand is rarely used because of the risk of the sand getting
dirty and causing infections. Since "clean" crabs are
essential for the work being done, this is helpful. But under aquarium
conditions a few cm of
coral sand and crushed coral would be very useful. Live sand is
obviously helpful in terms of water quality management, but the Limulus
couldn't care less either way.>
I also have Live Rock that needs a place to go. Can I put it in the
crabs tub or should I put it in a separate tub?
<Limulus don't like rocks. Plus, below 25 C, your expensive
Fijian live rock is soon going to die back. Would concentrate on
old-school canister-type filtration, ideally supplemented with some
aeration to keep
the water nicely oxygenated.>
Over the next few days I will do the research you propose so I
don't have to ask you so many questions!
<I'm no great expert on these beasts, though like Bob, I've
bumped into them a few times in the scientific side of my life.
They're virtually never kept properly by hobbyists, hence the need
to concentrate on lab reports.>
Right now, I am in a hurry to set up the crab's new home before
FedEx arrives :))
<You'll be fine. These are EXTREMELY hardy animals when given
essentially correct conditions. There is an Asian species sold as a
freshwater horseshoe crab that manages to cling onto life for months
conditions, even though it's a brackish/marine beastie. Don't
panic, do your reading, and enjoy.>
Re: Horseshoe crab arriving today
thanks again! I will give it my best shot!!!
<Good luck! Neale.>
Horseshoe crab arriving today 11/20/09
The horseshoe crab arrived healthy-looking and I set him up in the 100
gallon Rubbermaid. However, we can't keep that big tub in the house
(it's in the basement) and we just realized he is so cute that we
would like to watch him grow. So, I bought a cheap 14-gallon aquarium
and put about 1" of sand in the bottom of it and want to move him
into it temporarily until he outgrows it. The unheated water seems
stabilized at 68.7 degrees.
Since he is only 2" in diameter, will he be okay in this aquarium
At what size should we upgrade him to a larger tank (is there a size
per gallon formula we can use as a guide as he grows so we know when to
upgrade the size of his environment?)
<Not aware of any formula here. I'd use common sense. At its
small size, a 14 gallon tank is probably fine. But once it gets too
long to turn around easily (the long tail is an issue here) then
it'll need a new home. I don't believe these animals grow
especially fast, but they do eventually get quite big. A good size
specimen will have a body around 20 cm long, with a tail about as long
again. They can get bigger though.>
Lastly, this aquarium has two incandescent light bulbs. Is that ok or
does he need fluorescent light?
<Couldn't care less. These animals are nocturnal, and don't
particularly like bright light.>
Thanks again Neale.
<Happy to help. Good luck, and do perhaps send a photo along! I for
one would be interested in seeing this beastie in his new home. Cheers,
Re Horseshoe crab arriving today 11/20/09
Did you receive this email that I sent early this morning? Please
respond at your convenience. Thank you once again.
<Hi Dennis. Read it and replied. The answer is up on today's
Do check my reply didn't get thrown into your Spam folder by
Re: Horseshoe crab arriving today
wow, cool, i made the "big time"...
<As does everyone who writes... and when we tell them they're
nuts keeping Seahorses and Great White Sharks in the same tank,
they're not necessarily thrilled about seeing this on the Daily FAQ
seriously, thanks for your prompt response...i will send you a pic in
the next few days...
should i leave the light off permanently?
<Couldn't matter less. Ambient room lighting will be ample, but
if you want to use lights, then by all means go ahead and do so. Under
bright light, Limulus will hide, but a lower power tube like a GroLux
or a moonlight tube would be fine. Cheers, Neale.>
Will my horseshoe crab eat my other livestock? (RMF, feel
free to argue!) 10/15/09
Hello! I have read much of the information on this site and am very
impressed. However I don't see my answer, so here we go. I just
brought home a horseshoe crab from a guy that I was buying some live
rock off of.
<Hope you have a large coldwater marine aquarium to keep your
Limulus in; they are not tropical animals and cannot be kept in
tropical reef tanks.>
I got lots of live rock, a clown fish, 2 zebra fish and an enmity.
<An enmity? Do you mean that? An enmity is a hatred. Do you mean an
anemone? One of those big things with tentacles that looks like a
jellyfish stuck to a rock?>
Well I got the fish and crab for nothing so I took them. The fish are
doing fine tonight but the crab is all over the place, probably because
of the current.
<He's looking for a way out of this tank and into a coldwater
I didn't have much in the tank because I have only had it running
for 2 months or so and am kinda new to all this. So I decided to come
to your website and see what information you had for me! Well I
panicked when I seen that horseshoe crab eat shellfish!!!
<Up to a point. But they are primarily detritivores that feed on
small organisms and decaying organic matter they sift from mud. In
captivity, scientists maintain them by taking them from the holding
tank, putting them
upside down in a feeding tank, sticking some shellfish between their
legs, and amazingly enough, they eat the shellfish. Leave in the
feeding tank for an hour so they can defecate, and then return to the
holding tank. They do this 2-3 times a week. While it sounds a
performance, it's actually the best way to maintain Limulus for any
length of time outside of a very large public aquarium. In a really big
tank with a deep sandy substrate, they are to a degree
"scavengers" that get by on leftover food and such, but this
isn't really viable in home aquaria. We're talking tanks
measured in 1000s of gallons here, which isn't what most folks have
I Only had a few friends in the tank before tonight. They are 2 baby
brittle starfish (maybe 1in. diameter) a Emerald crab, 2 blue hermit
crabs, and a skunk shrimp. So immediately pulled this horseshoe guy out
of my tank and put him in my sump for the night (lots of rock there
with very little current and light). He's a little more calm there
but, I need to know if this new guy means trouble for my other little
helpers in my tank. I am trying to start slow, and do things right.
<He's actually doomed.><<I do agree. RMF>>
100lbs of live rock
2in of sand
<This is a weak link in the chain: you'd need a very big, very
mature deep sand bed to maintain Limulus "naturally".>
1 horseshoe crab
1 skunk shrimp
2 blue hermit crabs
1 Emerald crab
2 zebra fish
1 tomato clown fish
1 colony of mushrooms
Dose anything above NOT belong together in a tank
<Yes, the Horseshoe crab doesn't belong. It needs a large
unheated tank maintained at around 10-20 degrees C with a deep sand bed
it can burrow into. If you can see the crab, it isn't being kept
properly: in the wild they stay under the sand much of the time. There
are tropical species, such as Carcinoscorpius, but this species is sold
as a brackish-water "Mangrove Horseshoe Crab" and so far as I
know not in the US, since the American trade has access to the cheaper
Limulus. Even in Europe, Carcinoscorpius isn't often seen, which is
a shame because it's smaller, highly euryhaline, and consequently
easier to keep. Anyway, Limulus is one of those animals *not* to buy on
a whim. Hope this helps, Neale.><<Well done. RMF>>
Subject: another photo, please: blue-legged
> Hi Bob,
> Do you have this beastie? Clibanarius tricolor, or
> As a swap, I can offer a photo of Carcinoscorpius
rotundicauda, a euryhaline Limulus doing the rounds as
the "freshwater horseshoe crab" even
though it doesn't last long in freshwater (no surprise).
Will either of the attached do? B
Re: another photo, please: blue-legged hermit?
Yes, perfectly well! Thanks Bob.
Attached, a "freshwater" horseshoe crab.
<Will post w/ your prev. comment with credit to you.
FW Limulus, not! 8/29/2009
Here's a better caption:
"Carcinoscorpius rotundicauda, one of several Southeast
Asian Limulus relatives. Basic care similar to Limulus
polyphemus, except that Carcinoscorpius rotundicauda is truly
euryhaline and tolerant of a broad salinity (and temperature)
range. Sometimes sold as a freshwater invertebrate, as it does
sometimes occur in freshwater habitats, having been recorded from
the Hooghly River 90 km (56 miles) upstream.
However, it does not do well in freshwater aquaria, but can be
maintained in brackish or marine aquaria from SG 1.010 upwards,
assuming other factors (substrate, diet) are
Will append. B
Horseshoe crab and purple urchins...
OPublic'sMoney... mis-stocking 1/9/08 I work in a school where
we have recently (6 months) established a 1000 gallon touch tank.
<Nice> We have a large variety of damsels and starfish, arrow
crabs, one lemon angel, live rock, cleaner shrimp, sally lightfoot
crabs, flame scallops, <Poor choice with the scallops, have a
terrible survival rate.> spiny urchin, polka dotted batfish, and
about a dozen purple urchins and had two horseshoe crabs, about 9"
in diameter. One died about three weeks ago and the other this weekend.
<Not surprising, are cold water species and would have trouble in
the warm water required by the other residents. Please see here for
more http://www.wetwebmedia.com/hshoesys.htm > We added the urchins
about three weeks ago and wonder if they are the culprit.
<Doubtful> I fed the fish one evening on a weekend and found an
urchin attached over one of the horseshoe's eyes. The eye was gone
and the horseshoe was dead. Don't know which came first. <The
crabs death, urchin was just scavenging for a meal.> The second
horseshoe would not eat for me on Sunday of this week and on Monday it
was nearly dead and the urchins were attacking its eyes. <Easiest
part to get to on the crab.> Are the urchins the problem or do we
possibly have another issue? <Other environmental issues.> Is it
absolutely important for the horseshoes to be able to bury themselves
completely? <Does help them, but not the issue here.> Our sand is
not that deep. We now have two very small baby horseshoes that were
added before the big ones died, but we don't want the urchins to
get them too! <The urchins won't but the inappropriate
temperature probably will.> We were hand feeding the horseshoes
squid and brine shrimp and they were eating well every day. This was
advised by the supply source where we purchased them. <They should
have advised you that they need different environmental parameters than
the other inhabitants.> I can't find any source of complete
information on their care and would LOVE to have that information if
you can point us to it. They are wonderful for the tank and the kids
love them, but we don't want to just add another pair to have them
die again in 6 months. <The most likely outcome without a
specialized cold water tank. See here for more
http://www.wetwebmedia.com/horseshoecrabfaqs.htm > THANKS!
Re: Horseshoe crab and purple urchins 1/10/08 What is
the "ideal" tank temperature for Horseshoe crabs...
<Something comparable to the wild, i.e., coastline of North America
from about Delaware south to the Gulf of Mexico, but prime habitat is
the warm-temperate parts. Think somewhere like the Delaware or
Chesapeake Bays. So somewhat cool in winter, say 12-15 degrees C, up to
the low 20s C in summer. They aren't tropical animals, and their
lifespan is distinctly shortened kept under such conditions.> and
what is the ideal feeding arrangement?? <Again, just as the wild.
Deep sand/mud, where they process food by shoveling it past their mouth
as they burrow through. If you can see a horseshoe crab clear above the
sand/mud, it's an unhappy animal. They plough through the sediment,
and only really feed successfully when kept thus. They don't
"hunt" for food like regular crabs, sniffing out stuff and
gobbling it up. They're more like earthworms on land, in the sense
that burrowing = feeding.> We have our temp at 75 and had been
feeding our guys by hand daily either brine shrimp or squid and the
gobbled it down. <Too warm, and does need to be seasonal, with lows
in winter and highs in summer. Realistically, a room temperature tank
in a cool part of the building is the ideal, and anything else will
only shorten the life of the animal though heat exhaustion etc.> We
still have two small ones (2"). Is there any text you recommend
for reading? <Nothing much published beyond the article Bob already
referred you to here at WWM. In labs, where Limulus is often used,
it's a short-lived animal destroyed after the experiment is done.
New stock is invariably collected from the wild.> We are trying to
develop a "library" for our students as well as internet
sites they can research for information on our tank inhabitants.
<Much written on these animals, though mostly from biochemical and
physiological angles, since that's what these animals are mostly
used for. Not much on ecology, nor maintenance in captivity. Quite a
bit known on breeding, but mostly from field observations. Do searches
using its Latin name (Limulus polyphemus) plus those of the Asian
horseshoe crabs Tachypleus and Carcinoscorpius spp. Cheers, Neale.>
(RMF, feel free to comment) ... the root problem/basis of many
of our modern world's problems are derived, heated by their being
too much government... people, money... resources stolen, mis-directed.
Principally what we need is to do away with life-time civil servants...
Think on this. RMF... who does see this as pertinent... the money
mis-spent here...> Re: horseshoe crabs Hi I read the
paragraph it seems its directed at only one species. I'm not sure
what I have its light tan and about 2-3 inches in length I have about 7
inches in the back of my tank with lots of sand that he has left trails
through would this be a small one that don't get big or a gigantic
one? I told the pet store lady my tank was 30 gall long and she
recommended him? what do you think. Thanks guys for all my question.
<Most all anyone sees in the trade in the U.S. is Limulus
polyphemus... they do get large. Bob Fenner>
Horseshoe crab 3/19/04 I recently bought a horseshoe
crab. I've got him in my reef tank it consist of crushed
coral and sand , it is mixed about half and half. I was just
looking around the net and had read that they do not do well in
captivity because they usually starve. I also read that they
will eat different frozen foods that I can feed him but my main
question is that if they die do they excrete a poison like the cowfish
would when it dies. because I don't want it to harm my other stuff
in the tank. please help!! thank you Angie <Don't
worry about the horseshoe crab poisoning anything else when it
dies. Yes, they often starve in aquaria for lack of natural
food, but the bigger issue is that they are
temperate. Normal tropical aquarium temperatures are
therefore stressful to the point of being fatal. Best
Horseshoe crab Dear Bob, <Michael here today, not
quite as good, but I'll do in a pinch>
I live in Rockport, MA and I'm going
to set up a 20 gallon, room-temperature saltwater aquarium for local
species. It will contain local seawater and
sand. Some species I'm planning on having are mummichog
minnows, common periwinkles, rock gunnels, and hermit crabs. <Neat -
possibly some local alga as well?> I was wondering if a
store-bought horseshoe crab could survive in such a
tank. Horseshoe crabs are occasionally found in my area, but
are uncommon and usually large. I know feeding can be a
problem, but I plan to use local sand from the ocean full of living
things. I could also use native seaworms. If you
have an comments, or suggestions for other species that could survive
in such a tank, please reply. <Well horseshoe crabs
aren't all that difficult to keep alive, but they grow much too
large for a 20 gallon aquarium. The carapace of a horseshoe
crab can be 12" across> -Curtis <M.
Re: Horseshoe crab Michael, Thank you! I am amazed
by how quickly you responded. <Thanks, thought I'm not always
this vigilant> If the horseshoe crabs got to big,
I'll just release them where I've found others. <As long as
they're endemic to the area, and you release them when they attain
~5" they should do fine> Do you know any good sites
with horseshoe crabs? <I would search Google for some links for you
but this computer is going haywire. I hope I can even get
this email sent> Also, do you know if tidepool Sculpins
or cunner wrasse could survive at room temperature? Do you
know of any tropical species that could? <Depends what you mean by
room temperature. Most tropical fish will survive in 75-85
and do quite well> Thanks again -Curtis <M. Maddox>
Horseshoe Crabs I've recently ordered some small 1-inch
horseshoe crabs for an established saltwater tank (with a few
damselfish and a Hawkfish). <I do hope that your tank is quite large
(~180 gallons or more), as Horseshoe Crabs are unsuitable for life in a
small aquarium, even if they are purchased small (everything has the
right to grow, right?)> The bottom is mostly rocky now, so I'm
thinking I will need to make a sandy area for the crabs to burrow in,
am I right? <Yes, your assumption is correct.> How deep should
this sand ideally be for the crabs? <Depends on their size. At a
small size, I would think around 3" would be plenty. At adult
size, you may need a couple of feet.> Also, I've done a lot of
research about diet, and have gotten quite a variety of answers. In
your opinion, what works BEST with horseshoe crabs, and how often
should I feed them (I know overfeeding can kill). <They are
detritivores, so fish food/krill would work fine.> Thank you very
much-- these are such weird creatures that it's hard to find
specifics! <I'm glad I could help. Mike G> Horseshoe
crab I inherited a horseshoe crab. It has developed a black
"fungus?" on its back (near the tail). It is approx. 6"
wide and living in a 2 gallon tank...do you think it has outgrown the
tank? <Hello, the black fungus is probably algae that has grown from
being in such a small tank. A horseshoe crab that size needs at least a
120 gallon tank. Good Luck MikeB.>
Crustaceans And Damsel Death - 08/12/2005 I'm wondering
how my fish died; he was in a 10 g. tank. He is a neon
velvet damsel with 3 hermit crabs and horseshoe crab and a turbo snail.
<Way too much life for a 10 gallon tank.... Please see
here on horseshoe crabs: http://www.wetwebmedia.com/horseshoecrabfaqs.htm
. This animal is completely unsuited to your system.> I
had only had him for 24 hrs. and he was on his side. <Almost
certainly environmental. Be testing your water
regularly.> When the hermit crab saw that he went over there and
grabbed him so I took all the hermit crabs out in a small bucket with a
bit of water and they ate that entire fish but the head. When they were
done I put them back in the tank. Can you tell me if that was okay?
<Probably not a problem, in any case.> My horseshoe crab has been
buried for I think two or three days but has been messed with to see if
he was alive. <Likely not for long in your system....> He was
,then he just buried himself again. Can you tell me the proper care for
all of them? I would appreciate it. Thanks, Drew <All you
seek and more is already archived: http://www.wetwebmedia.com/marine/index.htm
. Wishing you well, -Sabrina>
Crustaceans And Damsel Death - II - 08/14/2005 I had read a
few of your listings on horseshoe crabs would a pet store buy on from.
<Might wanna proofread before you send, for future
reference.... I am *guessing* you are asking if a fish store
would buy back your horseshoe crab? Possibly, or possibly
would take it in trade for store credit. You will need to
check with your local fish stores; all of them vary in what they will
do about livestock.> I don't know too much on the subject,
I'm only 12. <Ahh, you're doing outstandingly for
12! Keep up the research, and you're sure to learn and
enjoy this hobby.> My hermit crabs are not big and neither is the
horseshoe crab. <The size of the crab is not what's
in question, just the pure unsuitability of it in any warm, small,
tropical reef system. The smaller the tank, the worse for
the horseshoe.> I have a little castle thingy and a little rock. I
have also been cleaning the tank and doing water changes once a week.
Should I keep on finding out if the crab is alive or to leave him
alone. <I would not mess with him any more than it would take to get
him to a fish store or someone with a suitable system.> I also
don't have enough money to get a bigger aquarium. <It would take
a very large, cool water aquarium to keep the little guy
alive. Were I in your shoes, I'd truck him back to the
store and ask for a refund.> I haven't been able to find out
about these little tiny things crawling on the glass is that bad or
good and what do I do about them? <They're more than likely
good. Probably copepods and other such desirable
animals.> Thank for all your help so far, you guys seem to know a
lot about fish. <The more you learn, the more you realize how much
more there is to learn! What a terrific hobby this
is. I'm glad you're getting into it so young.
I'd like to give you a few ideas for your tank. If you
stick with just invertebrates, like your hermits, and maybe a pair of
skunk cleaner shrimp, it'll probably be a very easy, very fun tank
to care for. There are a lot of neat, smallish crabs
(scarlet hermits, emerald crabs) and neat shrimp that you could choose
from to make your tank fun without fish. But you've got
the right idea picking a single small, hardy fish if you do want to
have a fish in the tank. You're on a great road to a
great start!> Drew <Wishing you well on this adventure of
Horseshoe crabs 10/5/05 I was reading on your FAQ's
about horseshoe crabs that they don't live long ..days
or weeks. I had kept them before in a tank without a heater
(room temp), and they lasted for years. I fed them black worms, and
I would put a little piece of fish under their shell. The
tank was fairly warm, but most of them did ok. <Eddie,
the general rule for keeping horseshoe crabs is a larger system with
fine gravel/sand and preferably cool water. As you say, they
are not hard to keep provided the correct conditions are
provided. James (Salty Dog)> Eddie
Horseshoe Crab selection, systems 1/17/06
off I have to say I did not do an extensive amount of research on
horseshoe crabs before I bought one (and now I regret that very much).
I went to one site that said they were easy to keep and ate matter in
the substrate. With this lazy-man information I went to my
local fish store and picked one up. In my obsession with my
new horseshoe crab I decided to do more research and came upon this
site (which I might add is very helpful). I feel really bad
for my horseshoe crab, I fear he will starve. <Most do> I have
only a 55 gallon tank, and about half the sand bed is covered with
rock. The temp is usually kept at 78 degrees Fahrenheit,
I'm aiming to lower it (would 75-76 degrees be good or still too
warm?). <If this is a/the (typical) coldwater species, (the Atlantic
U.S....) yes> His tank mates are one scooter blenny, one
royal Gramma, two peppermint shrimp, one emerald crab, and about a
dozen types of snails and maybe ten scarlet reef hermits. As
I now see I believe I cannot support one of these creatures with my
sand bed alone like the site said (oh yeah, my sand is sugar fine and
about 2"-3" deep, as of now the horseshoe crab is about
1.5" across and .5" tall) I'm also worried
about his health in the present, let alone starvation in the
future. When I first introduced him he had trouble getting
under the sand, he would go in half way, and then come out again.
<Good description> He was also very clumsy, crashing into walls
and the rock and sometimes flips himself over. I woke up
this morning, watched him a bit, and he was finally able to get under
the sand, but he's not moving, I can see the lump where he is and
he hasn't moved for about 2 hours. Is this normal?
<Do have periods of long senescence> Any way, if he does survive
*fingers crossed*, is there a way I can possibly feed him manually by
putting food under his shell? <Can be tried> Any other
suggestions on feeding are welcome, and what can I feed him to
supplement his diet of worms other things in the sand that will be
healthy? Thanks for your help! <What little I know re the captive
husbandry of these ancient arthropods is posted on WWM. Bob Fenner>