I have four fish significantly bigger than my red cap oranda, and it was happy in it's new tank for the first couple of weeks and recently, it has been hanging out at the top and has a clamped dorsal fin. I use sinking pellets and it only goes down to feed, almost as if it's avoiding the big fish, who all seem very happy. I have seen that when the little red cap goes to eat a pellet, the black moor would hover on top of it, then eat whatever the red cap oranda was trying to eat. I've read that clamped dorsals are a sign of sadness, so is it being bullied? How do I stop it?