First off I have no idea what gender my two angels are that are doing this, I'm a little concerned if its fighting but I'm not sure as it doesn't seem aggressive. The oldest koi is "kissing" or at this point nose bumping the gold one, only to have him/her swim away then swim beside then swim away. There are no torn fins, missing scales, signs of wounds, or aggression (unless the kissing is aggression). I tried to record the behavior but they stop immediately when I come close to beg for food.