Please help ID small crab

[horseflesh]

I found this crab shell in my tank this weekend. It's about 3/4" across. There's nothing like it in Shimek's book... anyone have an ID?

I have seen the critter before, but only once, and only part of one claw--he hides all the time. That is all I have ever seen of him besides this shell.

FWIW I have no unexplained death or injuries in the tank so I don't believe he is dangerous... yet. But I would like to be sure.

 

[LeslieH]

Can you provide a picture of the back? And do you know where your live rock came from? Indo-Pacific, Florida, or Caribbean?

 

[horseflesh]

I'll post another picture tonight.

As to where the rock came from... I believe mostly from Florida. I have a little bit of Tonga but it was pretty bare when I got it so I don't think it had any substantial hitchhikers.

 

[Paul79936]

There are something like 5,000 species of crab so forget trying to ID it by species. From looking at it I think it is carnivorous, judging by the claws.

I have had crabs grow amazingly quickly, so be ready to remove it if it becomes a problem.

 

[charlesr1958]

If its claws look like this, then it is any number of "cling" crab speices, which for the most part just scrape away algae on rocks. I have a large black one in my tank that I can not catch, but it has not done any damage in over a year now. If the claw tips are sharp and pointy, them it could be any number of xanthid crabs, which I would then remove.

Chuck

 

[horseflesh]

Thanks everyone!