Even though it is a big monster of a mollusc (3"), these critters are benign gentle giants that slide around the glass cleaning algae, much like the turbos. Unfortunately, in my move from the 55gal tank to the 60gal tank, I lost 2 of these great animals and was very upset. I now only have one, which I guess makes him all the more treasured. Even being a huge seafood fan, I would never think of taking my favorite mollusc out as a midnight snack!