Just keep a close eye on it, like I do with my lot...watch reactions with other tankmates. The ones I have in my tank just seem to tidy up around the place. I only get rid of the grey hitchhikers if they fall out of a rock or something. I think the main thing with my red and white crab is...I like watching him and his antics, He doesn't bother my fish or shrimp, he doesn't eat my corals...but I know where he is if need be.