Black Moor biting my white goldfish

Don't know why he would be doing that. If he's not doing any damage or really pestering him I don't think I'd worry too much. Maybe it's just a game they play, I don't think those fish could really hurt eachother badly. They might pester one another by chasing, pecking(which I don't believe is too hard with goldfish breeds.), and whatnot. It could also be that the black moore is attracted to the white goldy, as I remember something about mating rituals entailing nipping of some kind, although he is likely too young for that yet. Maybe he is attracted to the fish's color alone and he wants to get at it in some way. Let me know if any of my info helped or not.~Angela