Hey I just learned something! Glad I haven't come across one of these guys myself.
About 3/4 of the way through this article:
http://www.reefkeeping.com/issues/2003-04/rs/
Says find out which rock he's in, and flush him out with carbonated water. Interesting.
Sounds like he is your biggest problem, eating all your snails is adding to the bioload of the tank. I don't think there is a cube-equivalent for live snails.