A black emerald crab?

[jallard]

I have seen this A black crab which looks a lot like a black emerald crab. I havent been able to get a picture of him yet... he is pretty shy. Are there any good crab ID sites?

 

[charlesr1958]

I think I have had a few of what you are describing from time to time. While small, they don't appear to do much damage other than plucking off tiny inverts and algae off of the rocks, which I rather they did not. But as they grow, they always end up becoming trouble, most notably by plucking off a few zoanthids and running off with them, while scraping the rocks clean of all life at the same time.

A Hitch Hikers Guide to the Reefs

Chuck