I have 2 angels, 2 large and one small. The large angels leave the small one alone and never used to fight. In the last few days though they are fighting like crazy! The larger of the 2 has been hiding but the other scares him out of the cave and bites him repeatedly. His fins are frayed and there is a chunk of scales missing. One of his long front fins is almost gone. I've been feeding a lot of frozen food lately... is that whats causing this sudden aggression? How can I stop this aggression? Will adding some dither fish like danios help? Will his front fin grow back? Should I take any precautions like medication or aquarium salt because of the missing chunk of scales?