IMP They are more trouble then they are worth. I have had a couple of different species. They can knock down small rocks, eat snails and starfish, they crawl over everything, distrubing leathers and possibily pulling up pulps. But I have still always been drawn to them. They look cool and eat coraline alega. If you do decide to get one, I suggest getting one as small as possible, to reduce the risk of any disturbance.