We bought what was supposed to be a mated pair of blacker ice clowns back in the beginning of april. They have been doing great since then. Recently as they have matured, one has gotten about twice the size of the other and has started chasing and nipping at the smaller one. to the point the smaller one is starting to get a little pale and the edges of his fins are a little frayed. They are both eating well and the aggression doesn't seem to be about food or during feeding at all. it almost seems that the larger one (the female?) is trying to keep the smaller one down in the corner of the tank. Is this normal behavior for a mated pair as they mature and one tries to gain dominance? or is this a negative behavior that I need to look out for and try and separate them?