Well,how big's the tank?
Bala basically get along with everything (they do better in a group though),so you could put them with anything your heart desired (within reason) except another "Shark" species that is aggressive (Red Tail?... ouch).
I've seen them with everything from Ghost Knifes to large cichlids to Arowana.
Several I know keep them as "dithers" in their larger 180+g cichlid tanks.... and are quite common with Oscars (proper sized tank of course).
Long as you realize they grow 12+" and like to be in at least 3's,then you can about chose anything.