Mystery crab

[God of thunder]

Hi there.

I didn´t know where to post this so here goes.
Last night i spotted a crab in my LR. I´ve never seen it before, it was about an inch in diameter, it looked nothing like a hermit, more like this.....
http://www.whoi.edu/science/B/people...x/CrabShot.JPG

But flatter, not as tall that is.

Can you experts identify it?

[widmer]

emerald?

[crusing52]

I would guess emerald also. I had one for a while. It will become aggressive if you don't feed it.

[God of thunder]

How big do they get? do i need to worry about him attacking fish, crabs or shrimp? are they reef safe?

[LeslieH]

Does yours have the same prominent eye stalks and body shape? Then it's in the family Ocypodidae. These are mud & sand crabs typically found on the beach or in shallow water. They eat small detritus particles & algae from the sand and are reef safe but at the same time, are not good candidates for a reef tank. If it doesn't have the eyestalks and has a chunky body it's probably a xanthid of some sort.

[God of thunder]

Why are they not good for a reef tank?