Please help me identify this

[copenhagen_cowboy@live.co]

I found a tiny little crab about 1/4" in my acrapora today. I couldn't tell if it was just hanging out or picking at it so I pulled him out and he is floating in a ziplock in my sump. He has a white claws with red tips. The head is black then fades to a red body and rear legs.the photo should be attached to this post as well. Thanks