What kind of crab is this and is it a danger to my tank?

[Mavericks]

I have never seen this crab on the rock. It just digs around in the sand. Pretty cool to watch him going about his chores but if he is a danger to my reef tank I will have to stick him in my refugium.

 

[anthonygf]

Sure is well camouflaged. Can you get a shot of his face?

 

[Gtinnel]

At first I though this was one of those can you find the crab pictures.