Look, this tank has been thoroughly discussed in the other thread. It is overstocked and overcrowded with unsuitable fish. You are going to have to look at rehoming most of the fish in there or there will be more and more of these incidents.
As for the bala, how bad is his bite? You may want to add some stress coat or melafix to help him heal. It is also essential to keep the water very clean to keep the wound from getting infected.
edit: In your other thread you said "why the h*ll can't you experiment?". Fair enough, you are experimenting and this is what happens.