Crab Identification

[GTfish]

I've got crabs!! Two red crabs and one grey crab, all about 1.5 inches long, came in on my live rock. They appear to graze on the live rock- do they eat corraline algae? I cannot tell if they have caused any damage yet. Picture is attached below; I want to remove these guys if they will cause problems. Pictures of these crabs/my awesome liverocks.com rock are at http://www.mschork.com/Pictures/albums/FishTank
The lr is somewhat sand-covered at the moment; still working on that. Thanks!

 

[jackdp]

That crab looks evil, almost everyone will tell you to remove the crab regardless of ID and that they always have the potential to cause problems.

 

[Atari]

Eeek! Get that thing out of there ASAP! 8O

EDIT: Although it does look a bit like a Mythrax crab.. hmm.

 

[Sea Cat]

I have 3 of those crabs in your pic there.
They came on my live rock, and seem to eat things on the rock.
They look just like an Emerald Crab, except not green.
So, I would assume they are pretty much just as safe as the Emerald Mithrax.

Although, I have glimpsed a little guy popping out of my LR that has a bigger claw on one side. Still trying to catch that little guy.

 

[Zack]

I have servel. they are just scanvenges and I keep them in my reef tank.

 

[lziarek]

i have heard that crabs that have saucer like pincers (same as emerald crabs) are harmless scavengers and mainly eat algea. I too have recieved some in my rock shipments from lr.com (btw awesome rock!!!) and plan on keeping them until they become a problem. I also have some sharp pincered crabs but they have been keeping to themselves lately. My aquarium is an innocent until guilty establishment (except mantis shrimp). =)

 

[Sea Cat]

My aquarium is an innocent until guilty establishment (except mantis shrimp).

LOL!

 

[yaksplat]

I've had one of those in my tank for 6 months now. All it does is pick at the LR.