FAQs about Micro-Crustaceans
Related FAQs: Microcrustaceans/"Pods" 1,
Crustacean Selection, Crustacean Behavior, Crustacean Compatibility, Crustacean Systems, Crustacean Feeding, Crustacean Disease, Crustacean Reproduction,
Copepods, other Small Shrimp-like ID 1,
Small Crustacean ID 3,
Small Crustacean ID 4,
Pod Behavior, Pod
Compatibility, Pod Selection,
Pod Systems, Pod Feeding, Pod
Disease, Pod Reproduction,
Amphipods, Copepods, Mysids, Brine
Shrimps, Banded Coral
Mantis Shrimp, Anemone Eating Shrimp,
Micro-Crustaceans, Amphipods, 'Pods: Delicious and
Nutritious By Adelaide Rhodes,
PhD, Copepods, Mysids, Hermit
Shrimps, Banded Coral
Anemone Eating Shrimp
Unknown animal in my reef tank.
Hi about 3 weeks ago I noticed about 100 tiny creatures in my
Looked like a really small string. Most were brightly colored
about 1/4" to 3/8" long and about 1/32" wide.
I figured it was either bristle worms or some other worm that must have
been in the live sand I added to the tank several days earlier.
Now I those guys are about 1/2" long and look like tiny shrimp. Antenna
and the curled tail, and the bright color is gone. They only come out at
night. And are fast as he'll when it comes to getting out of the
What could it be and if I need to get reed of them how do I do it?
Mainly I'm worried if it is a mantis shrimp. I got a lot of small fish
that could suffer in the long run. I'm attaching some pictures. I also
got videos of the darn things if that would help identify them.
<Are all their legs about the same length? Am guessing these are
|Re: Unknown animal in my reef tank.
They were to small to tell for sure but from what i could see they have even
length legs. Do amphipods have multi color larvae? How big will they get?
<Larvae are very small; not visible to the naked eye... the ones you sent
pix of, described may be full size. BobF>
Hello everyone, just hope you could help identify this thing.
It is in a 29 gallon Bio Cube that I am using to cure rock. This
Bio Cube was used for a few years until I moved to a larger tank.
I left the media and the sand and a few love rocks. I am now
putting some base rock in the tank to cure before I add it to the main
<Mmm, let's see; all legs appear similar... Think you've got an Amphipod
here... aka a scud. Bob Fenner>
|Re: Identification 9/4/12
Is it normal for them to be so large? If they stay in the tank with
nothing to eat them could they get out of control?
<... search and read on! B>
Assistance identifying micro-crustaceans
Hello W.W. Crew!
Your sight has been an invaluable resource for me over the years
and I must thank you for saving my sanity on a number of
<It may have cost us some of ours!>
While observing my 5 month old reef tank (warm water at 80
degrees) I decided to grab the magnification lens off an old
night vision scope and do some looking around. I spotted
something I had not seen before, nor could I find a creature
similar in description or form on the web. The creature in
question has a jet black shell with a slightly lighter edging and
eight clear legs.
<A good clue... I could only see six... thought this might be
The clear legs are set in the fashion of a crab with four on each
side. It walks sideways like a crab would and when changing
directions it leads with either side (think crab running across
the beach, not hermit).
<Also a good clue>
I can see no antennae. It (micro-crab?) Is so small that these
are the only features I can make out without a microscope. The
main body looks smooth, with no segmenting aside from the legs.
It is barely visible to the naked eye being smaller than any of
the adult harpacticoid copepods I've seen, at what looks to
be about a third of the size.
I was told to look up "black reef bugs" similar to the
dreaded red bug but these just do not look the same in any way,
shape or form. To me (the ever so Untrained eye) they look
exactly like micro crabs.
<Might be... or just juveniles of same... should have ten
legs... but these others may not be so obvious>
I've attached the best image I could get of the mystery
creature and would appreciate any assistance you could provide
Please let me know if any other information is needed :)
<Just a better resolved image...>
<And you, Bob Fenner>
|Pod ID 5/15/10
Hi WWM Crew,
I have these white ants crawling all over my tank. They are usually
by the algae areas of my back glass, rocks, and crawling on my frag
rack. I believe I know what they are but would like to get a
positive ID from you guys. I pulled out some LR and let it out to
dry and some dead pods came out. They actually look bigger when
they are dead than in my tank. Can you ID these guys for me? Please
see attached picture.
<... need a much closer, better-resolved image... Likely
Amphipods... See/read here: http://wetwebmedia.com/podidfaqs.htm
and the linked files above. Bob Fenner>
I have had a lot of these pods roaming around but since I added my
green mandarin I see less now.
Tiny Bugs 3/21/10
Hello, I have these tiny 1/4mm copepods/amphipods living on my Ice Fire
Echinata. Unlike red bugs and Nudibranchs these guys are very fast and
run around often. Polyp extension never seem to be effected, and color
was good, but to be on the safe side I dipped the echinata in
Lugol's, and killed a ton of the little guys, but after a week they
are back. I don't see then on any other Acro in the tank. I hate to
stress out my echinata if I don't have to, do you think they are
<No way to tell from here>
Any input would be greatly appreciated.
<I'd try the patience route here. May well be harmless to your
coral/s. Bob Fenner>
Copepods or Isopods? 10/29/09
<Hello, Lynn here this evening.>
I have these tiny white dots on the glass. They congregate in the
corners of the tank. I think they are too small to be Isopods.
When my tank cycled I went 45 days with live rock and 4000
copepods as the only thing in the tank. There are tons of
copepods in the refugium. I attached a picture but it is hard to
make out because they are so small. Hope you can help.
<Unfortunately, I can't see the critters in question well
enough to be able to offer an ID but the good news is that
they're most likely harmless. Please see the following link
for photos/information regarding the most likely candidates:
Take care, LynnZ>
Help... ID, small crust., sans pix
Recently I started noticing these very fast swimming things in my 200
gallon swim tank. They swim and glide from rock to rock. They are very
tiny and fast but when I do get a glimpse of them they have a body like
a shrimp, are pinkish in color and have neon eyes. They are too tiny to
take a picture of them. They are not Pods because I have several of
them and different sizes, i also have a bunch of baby brittle starfish
and some tiny little starfish. I was wondering if you would know what
these are. Thanks!
<Mmm, not from the description... but do read as some sort of
crustacean by your description. Please peruse here:
and the linked files above, and send along some well-resolved images
when you can. Bob Fenner>
Mantis Shrimp Reproducing in My Tank? Nope,
Gammaridean Amphipods - 4/6/09
<Hi Samantha, Lynn here this evening>
I bought about 160lbs of live rock from the Gulf of Mexico about
3 months ago. I have already caught 3 (what I think are adult)
There are many more still in the tank, at least 5 more, that I
have seen. The tank is 300 gal plus a large sump.
This afternoon I found a little shrimp on the wall amongst all
the hair algae and other debris. I only wipe the front for a more
natural tank. There is what looks like an algae cocoon but open
on one end with a baby mantis shrimp in it. He wiggles and moves
up and down but looks like a larva. I am attaching a couple
pictures to hopefully figure out what the heck is going on I have
had some fish and shrimp come up missing, and I think it might be
possible because everything else is growing in my tank... why not
a baby mantis shrimp... please help.
<Sure thing. The good news is that what you're seeing is a
harmless, beneficial, and extremely common little hitchhiker
called a Gammaridean amphipod. We have a lot of information on
them here at WWM: http://www.wetwebmedia.com/amphipodfaqs.htm
(also see related links at the top of the page),
<You're very welcome. Take care, LynnZ>
Question about New Unknown Inhabitants
03/06/09 Greetings All, <Hey Chris.> I have an
interesting group of new unknown inhabitants to my tank. My tank
specs are as follows: 3 month old 20 gal. marine system, .021 SG,
<Too low.> T5 (1white 10,000, and 1 actinic) Lighting, low
water current. My current inhabitants are a single green
Ricordea, 10 blue-legged Hermit Crabs, and 3
"Margarita" Snails. Ok, I know bad idea on the snails,
but they all died within the last few days. My mystery guests
"arrived" about 3-4 days ago. I like to keep my tank as
clean as possible, so I am always on the lookout for algae
buildup starting on the glass. I noticed that about this same
time, the water started looking a little bit on the cloudy side.
By the next day, I happened to notice these little guys crawling
around on the glass, rockwork and some even floating around in
the current. They are extremely small, I would guess 1mm long and
1/2mm wide. They are fast little guys. I caught a couple of them
with an eye dropper and examined them under the microscope.
<Good for you... having a microscope.> The attached picture
is a rough "sketch" of what they look like (I don't
have a camera). Pardon the sketch quality. I don't think mice
were meant to be used for drawing lol! Their speed may be an
important factor for identifying them, so I'll mention that
when I was trying to catch one with a micropipette, it would keep
darting around rapidly in the sample container. The only other
thing that I can think of mentioning was that just before the
snails started dying, they would climb to the top of the tank and
sit above the water line for a day or so, and then fall to the
bottom of the tank. I would turn them right side up again, they
eventually stopped moving altogether. <no good... these are
generally colder water animals> I hope I've given you all
the relevant information to help with identifying these little
guys. If they are larvae of one of my three inhabitants
that's perfectly fine, but if they're pests the I can
figure out how to deal with them. <From your nice sketch, my
guess is copepods. Please see here:
Thanks so much for your time! Chris
|Re: Question about New Unknown Inhabitants
03/07/09 Thanks so much for the quick response! Also,
thank you for catching my too low SG, I'm going to slowly raise
it over the next several days to a more appropriate level. <Ah
good> That is wonderful news about the copepods! I read the link
you provided, and from the descriptions it contained, and further
researching the web and locating some pictures...you called it
perfectly!!! It's a huge sigh of relief that it wasn't some
nasty parasite. <Not to sound at all
"maternalistic"... but I am truly "proud" of
you for having a microscope! You are ahead of the rest. And yes,
they are actually quite wonderful and beneficial creatures... do
cherish them.> Thank you again, you guys (and gals) are the
BEST! <Hehe, thanks!> Chris Sara M.>
Critter ID: Gammaridean Amphipods 12/15/08 Hi
there, <Hi Aaron, Lynn here this evening.> I was just
wondering if you could identify these small critters, (about
1/4") that I get out of my filter pad about every 4-5 days.
<They're extremely common, harmless, beneficial little
detritivores called Gammaridean Amphipods, or scuds.> It's
from a 125 gallon reef ready saltwater tank. Live sand, live
rock, small animal load, bio-rocker filter in a 29 gallon
aquarium sump. If you need more info please let me know.
<Thanks to your very nice photos, I believe we're good to
go.> I would just like to know what they are, <Fish food!
Seriously, fish love to eat these little guys.> how they get
in my filter pad, <After hitchhiking in on live
rock/macro-algae, etc, they get there through the circulating
water and tend to stay because it's a nice, safe, food
pantry. Those filter pads collect all sorts of detritus - fish
food/algae etc, particles that the little critters thrive on.>
and if they are good or bad critters. <They're very good -
all part of the biodiversity of a successful system. For more
information, please see this link:
http://www.wetwebmedia.com/amphipodfaqs.htm> Thank you
<You're very welcome. Take care, Lynn>
Re: Critter ID: Gammaridean Amphipods
12/16/08 <Hi Aaron!> Thank you for your help..
<You're very welcome.> I'm so glad to hear that
they are nothing bad.. <Yep, that's always good news,
huh!> So just to clarify, you say they are beneficial. So does
that mean I would benefit by removing them from my filter pad and
placing them back into the main tank, for either food or as a
detritivore??. <Yes. I wouldn't be too obsessive about it,
but I'd return any that were obvious and easily
accessible.> I am still confused on how they get in there.
<Heheee! Teeny, tiny transporters ï¿½ Beam me
up Scud!> My rock is over 2 years old, and they are only in my
filter pad, I don't see any in the tank. <Ah, but have you
taken a look at night? These poor little guys are prey for so
many fishes that they generally hide during the day and venture
back out only under the protection of darkness. I bet if you take
a look in there tonight with a flashlight, about an hour or so
after the lights are out, that you'll see all sorts of little
critters scurrying here and there!> Thank you so much Aaron
<It was a pleasure, Aaron. Take care, Lynn>
|Parasitic? Nope, Good Guys: Harpacticoid Copepods --
10/28/08 Hi y'all! <Hi there!> I wanted to know
if anything in the photo is parasitic and/or if you could identify
them. <Unfortunately, I'm not sure what the worm-like
creature is, but I seriously doubt that it's anything to worry
about. As for the two creatures at the top of the attachment, those
are harmless/beneficial little Harpacticoid copepods. For more
information, please see the following links:
These were barely noticeable to the naked eye. These samples were
taken from quarantine tanks. <Yep, Harpacticoids are very small
indeed, even by copepod standards! Very nice photos, by the way!
Take care, -Lynn>
|<<cool pics!! -Sara M.>
Flame angel killed by sunk clown? And mystery small
crustaceans -- 10/02/08 Aloha :) Is it possible
for a sunk clown to injure a healthy flame? <Mmm, yes... a large
Sunk/Skunk clown could> Tank is 500 liters and heavily understocked.
<Interesting terminology> I had the flame since 2 years and had
taken him from a fellow aquarist who had him for 3 years. He was
healthy and was the aggressor. <One> After around 6-7 months one
day I see him missing a bit of tail and then in a day or two I see fins
ripped off. <Yikes!> Even then, He would swim in and around the
clowns territory without being bothered. I tried to catch him briefly
to quarantine him but he just hid himself. Next day I see my small one
inch mud crab(maybe mud crab) eating him. Had eaten almost half the
body overnight. <Yes, happens> My clowns are a bit edgy after
that. Next day I see the crab on its back. I was in one piece except
the flesh inside. Did it molt or is it dead ? <Can't tell from
here> I have had 2 mandarins and a baby blue tang disappear before.
<Mmm, this crab may be too much...> Seems a bit far fetched for
either the crab or the sunk injuring the flame angel? <Not to me>
Or do I have a mantis shrimp or some other predator? <Could be>
Another question. My tank is crawling with pods. They are always seen
on the glass and big ones on the rocks. Small ones are around a mm and
big ones are around a cm in size and white to transparent. Some are
even flowing in the currents. They are pods I believe as I see them
moving and have seen them using a magnifying glass. Both my mandarins
died and sometimes my Palythoa don't catch them either. What's
the deal? <Perhaps they are "too tough", smart or
unpalatable... Even may be "not what you think", predatory...
Any chance for you to catch, take some high-res. pix of these, send on?
Bob Fenner> Cheers