fish don't play. it is aggression. balas are semi aggressive. if the fins of the less dominant fish are not ragged from getting nipped, they will probably be fine. chasing is relatively harmless, fin nipping can end in death from stress and infection. i have never noticed balas nipping, just lots of chasing. if you see ragged fins, prepare to loose either the aggressor (buy removeing it) or the subordinateÂsurvival of the fittest. i have noticed that many schooling fish are very aggressive to members of their own species when they are in small numbers. like people, gravitate to each other, but fight when we are together.

i have a yoyo loach who gets aggressive during and immediately after feeding too. the food seems to bring it out.

sometimes the more plants can help as it breaks up the outline of the other fish making them less visible. my take is heavily planted, but the loach still chases after anything that he sees for about 10 minutes after feeding then goes back to foraging or hiding under the wood. my white clouds tend to fight and occasionally kill each other.

good luck