Right now he's just hanging out but if he starts messing with anything he's probably going to find a new home. As long as he's doing his part cleaning up and doesn't overrun the tank, I'm good with it.
Everything I've read online says the same thing. Handle with gloves.
Right on...they can sting, but the big ones are the worst. Can grow up to 4-5"
I don't like them, but they don't really harm anything as I can tell. The wrasse patrol in my reef eat them. But they show up in the algae scrubber and refugium.