I got a full size blue damsel from a fellow reefer that was giving him away, i thought it would be a good idea to put it in my sons tank with his clown, which is still pretty small, well after being in there with him for around 8 hours i fed them and he started beating up the clown pretty good and took a little chunk of his tail off , i transferred the clown back in my main tank, which he was in before, my question is what type of fish could i put the damsel its a 15gallon tank.