I have one right now in my 75g. Came with the (used tank) setup and I threw him back in when I moved the tank. I've spent the last week tearing apart the rockwork to get him out after he kept eating my new toadstools. Never bothered my palys or mushrooms, but new finger leathers would be moved every night and toadstools were ripped off of their superglued posts and nibbled on. Lobster is out now and no problems with my corals for several days. Never noticed a problems with snails or crabs. Only would see him at 3am with a flashlight. He is currently in the refugium in my sump and I am going to make it a nice home for him with a DSB, some LR, and daily feedings.
Eric