+1. Lemonpeels have about the worst reputation for nipping. IME if the clam is healthy and well established and was pre-existing in the tank before the Regal,there is a good chance the Regal won't nip. But of course there is no guarantee. It seems when clams or corals are stressed they give off an olfactory signal of some kind that triggers nipping. Once fish start nipping it usually leads to the demise of the stressed clam or coral.