Really you should only have one fish of this type per tank, although they all have different colour paterns they are basicly the same fish and have the same mannerisms. I made a mistake when i had 2 flying fox which only just tolerated each other, i then bought a red tail shark which at first was shy of the flying foxes but it soon got to the top of the pecking order and teamed up with one of the foxes to bully the other fox. I gave one of the flying foxes away before it was killed, i know have one red tail shark and one flying fox in a 290L tank with plenty of cover, they dont get on espesially at feeding times but the rest of the time there not too bad but i know at some point one will have to go!
The bala shark is different from the others and needs to be in a large group in a very large tank!