Crab Hitchhiker ID?

[tlhood]

Was walking by my tank while the moon lights were on and noticed this guy sitting out on my rock. He seems pretty shy, runs into a hole when he sees me around, which is why I had a hard time getting a picture.

He was picking on the algae on the rocks, and doesn't seem to be irritating my snails and hermits. He's got no hair, and he is a light blueish colour with stripes on his legs. Should I try to catch him? I'm looking to put corals in the tank.