I recently purchased a pair of bala sharks. i could instantly tell one was sick from the moment i put it in my 30 (thanks petsmart) and unfortunately died by the next morning, but the other is very healthy and has been for a few weeks now.
the only thing that seems a bit off about the bala is that it doesnt feed much really when all the other fish swim to get their flakes etc. i never see the bala eat the flakes. ive only seen him eat the freeze dried bloodworms i put in there on occasion. he may be feed off of fallen foods though because he has not sickened or declined in health in the least.
so my question is: is this just how balas regularly eat? should i purchase some specific foods? is it because balas are schooling fish and there is only one in my tank?

Let me google that for you