Uninvited crab in live rock

[jaymes]

I have had my 55 gal tank set up since Christmas. I have about 50 pounds of live rock. I found it so exciting to see all the things that came on the live rock especially since I didn't have much of anything else in the tank for months. For about a month now I've been noticing a strange looking crab. Sorry - no picture. The best way I can describe it is it looks like a crab you would eat only about 1/2 " across the body and the legs have some hair. The front claws are larger than the other 8. And it basically blends in with the rock as far as color. I have searched the internet trying to figure out what it is. I haven't found a picture that looks like it. I'm concerned whether or not it is a preditor. Any ideas?

 

[ags]

What you described sounds like a gorilla crab. Often found as hitchhikers in Florida gulf rock. They have the same body style as an emerald crab but with spikes of hair covering their bodies. Their front claws are large, they are part of the stone crab family, and will eat anything including other crabs, snails, shrimp and fish. I would post a picture but the last one in my tank has proved quite elusive. I suggest taking the crab out and giving it to your LFS or if you live near the water throw him back. I happen to live in Tampa where most gulf rock comes from and live on the water so I just toss my back. Hope that helps and good luck catching it. I think there is a website I can direct you too with pictures. If you are interested email me at agliabd@aol.com.

 

[agro]

I got my rock from the gulf. Here are the crabs that came with mine, and what I was told about em.
#2 is a red mithrax - red smooth body, with hairy legs - good
#4 unknown - grayish, hairy all over - probably bad

 

[rook]

I too have some unknown crab in my tank. I have only seen it twice in three months and I have not noticed any problems yet, but I still would like to get rid of it.
How do you catch on of these suckers??
Anyone else have any pictures??

 

[fishies]

I have an unindentified hairy crab in my rocks too. Also known as the 'rock monster' He's not the prettiest to look at and, he's been there since I can remember. All he does is pick at the rock, and hasn't caused any harm to anyone else in the tank. All though I did see him picking at a bristle worm before.

 

[skierguy]

I would use extreme caution in “throwing anything back in to the sea” I don’t know if you are aware of the massive problem in the Mediterranean with a macro algae bread for aquarium use
“Bred for its beauty, fast growth, and tolerance for cold, the "aquarium strain" of Caulerpa taxifolia, a bright green seaweed with fernlike fronds that is used to decorate saltwater aquariums, "escaped" from human control in the 1980s and has spread like a cancer through the Mediterranean, overwhelming native species and habitats. In this time line, written by Alexandre Meinesz, the marine biologist who has fought for years to warn authorities in France and elsewhere of this growing menace, follow the disquieting trajectory of this "killer alga" as it colonizes new waters around the world. Unless otherwise noted, "the alga" and "C. taxifolia" refer to the aquarium strain”
http://www.pbs.org/wgbh/nova/algae/chronology.html
Although we may have the best intentions IMO we should never let anything back into the wild that we did not take ourselves from the wild, we do not know what problems we may cause.

 

[tigs]

Originally posted by Skierguy
"bred for its beauty, fast growth, and tolerance for cold, the "aquarium strain" of Caulerpa taxifolia, a bright green seaweed with fernlike fronds that is used to decorate saltwater aquariums, "escaped" from human control in the 1980s and has spread like a cancer through the Mediterranean, overwhelming native species and habitats. In this time line, written by Alexandre Meinesz, the marine biologist who has fought for years to warn authorities in France and elsewhere of this growing menace, follow the disquieting trajectory of this "killer alga" as it colonizes new waters around the world. Unless otherwise noted, "the alga" and "C. taxifolia" refer to the aquarium strain”
I saw that special on PBS a few weeks ago. It was incredible to see the taxifolia cover so much of the ocean floor. It looked like hundreds upon hundreds yards of just green algae forest with no other colors present but green.

 

[ags]

ok, maybe I should have stipulated that if you don't live in the same region don't throw it back but like I said as to my situation I live in Tampa, Florida where the gulf rock many of us have is farmed. For me the gorilla crab is native to my backyard so throwing it back is no more or less harmful than me dropping a line in the water, catching a fish, and thowing it back. But I agree 100%, if you don't live where it came from maybe that is not such a good idea. Good with option 1, donate it to your LFS. Someone with a species tank might love to have it.

 

[jonthefb]

the florida aquacultured live rock that i just ordered in to our lfs, had one peice with an urchin, porcelain crab, and varity of snails all on the same piece of rock....needless to say i took t as soon as possible, all but the urchin!
good luck
jon

 

[jaymes]

Thanks for all the good info. As I read the postings I realized I might have left out a valuable piece of the crabs desciption - the back 8 legs are quite a bit longer than the rest of his body. In fact, until I saw the front claws and body, I thought it was some kind of sea spider. I have checked out the spider crab pictures on the net - but I still can't say I've seen one that looks like mine. I am having trouble finding info on the gorilla crab, too. I really wonder how I would get rid of this thing since it is so elusive and runs away as soon as you make eye contact!

 

[ags]

Given that piece of information I don't know if it fits the gorilla crab description. If you don't know what an emerald crab looks like do a search on this website for a picture. Gorilla crabs look indentical in body shape as an emerald. The only exception is color scheme and the presence of spikes of hair covering the body. The coloring on a gorilla crab is brown, tan, white and pinkisk color. The ones I have pulled out of my tank blend in extremely well to coralline covered live rock.

 

[rook]

AGS,
The crab I have may be a gorilla crab. How do you get them out of the tank? I never see it and definately never get a chance to grab it. Also, do you have that website that talks about gorilla crabs?

 

[ags]

yeah email me though because it is an online distributor and posting those types of websites is against this boards policy.
agliabd@aol.com

 

[jaymes]

This weekend I got a much better look at the crab. It's large front claws have dark tips. The "hair" is really much more sparse than the gorilla crab and isn't on the body. I'm wondering if it could possibly be a baby stone crab. Does anyone know about them? Or have any of you gotten stone crabs on your LR?

 

[vibe]

sounds like an emerald crab to me.

 

[zeppelin]

Originally posted by Jaymes
This weekend I got a much better look at the crab. It's large front claws have dark tips. The "hair" is really much more sparse than the gorilla crab and isn't on the body. I'm wondering if it could possibly be a baby stone crab. Does anyone know about them? Or have any of you gotten stone crabs on your LR?
I got allot of crabs in my FL live rock. Most are stone crabs. They are pinkish/red with flat, not pointy, claws. Some had pointy claws with dark tips. A couple friend that saw them said they were gorilla crabs, and B-A-D. I had about 10, and am down to two. Had to resort to spearing them to get them. They were too fast to catch and kept heading back into the live rock holes. Only time I can get at them is after the halides go out and just the actinics are on. Good luck.
Larry

 

[jaymes]

So how can I be sure it is B-A-D? I haven't seem evidence of trouble. Or would a snail dying and a few hermit crabs dying be sign enough? Do you always just listen to a fellow aquarist? If that's the answer, then I need to start hunting! I would hate to lose everything to that crab!

 

[ags]

I won't go completely out on a limb on this but will tell you the chances of having a stone crab in your tank are extremely remote. First they are big as in edible big (and extremely delicous and expensive) and second they have zero hair. Now you could have a crab in the stone crab family, like the gorilla crab. Again I could be wrong but in my unprofessional opinion I doubt you have a stone crab.

 

[vibe]

i still think its just an emerald crab. small, semi big claws, and hairy legs. sounds like an emerald in my opinion.

 

[wolffam]

I have two crabs, both the same type, both hitchhikers. One I caught and is in my sump the other is still lose in the tank. Looks almost like a rock when not moving. Lives inside a hole in the LR. Legs roll up under the body, claws are larger than the legs, but also, roll up to the front. Appears to have redish eyes and at one time had two white strips that have since disappeared. I have only caught mine eating the hair algae in my tank. One day I'll try to post a pic, when I can get a good one.