I have a FOWLR tank, about 6 months old. Found this tiny crab (about the size of a dime) in a piece of live rock I got this week. Picked up the rock since it was the preferred home of the Red Sea Mimic Blenny that I purchased. I have heard such bad things about crabs. Can anyone ID it and tell me if I should get him out of there? He is not hairy nor bumpy, pretty smooth and grayish in color.