Crab hitched a ride??

[DukeB]

Last night I noticed a crab crawling around on a peice of live rock. I didn't get to see him for too long, but he was green in color and about the size of a looney. To me it looked like an emerald crab. From what I have read, they can be a real pain in a reef aquarium (?).
So... if I want to evict hime from my proposed reef aquarium, how do I get him out?
Thanks in advance,
Duke