I have a tank with a small lionhead goldfish, a small black moor, a shubunkin, two minnows and a guppy. The guppy chases the lionhead around, nipping at his back. If I didn't know better I'd think he was cleaning him or something, but I'm worried that he's attacking him. As you probably know, lionheads aren't exactly olympic swimmers, so he can't really get away very well.

Is this a problem, and/or should I stop it...one way or another?