How long do the ones you have usually live? I'm not trying to be mean but from everything I have read they should be in at least a 125/gallon (I beleive that is for just one even), and should grow to be at least 14"-15" and live for years.
Look at thatpetplace.com they are called tri colored shark there, or at ****************.
If you really have had them for years..you actually are making me feel much better about myself, I do have 3 but was feeling so guilty that all I could upgrade them to for now was a 55 gallon. Believe me I had WAY to much fish for my tank in the begining, now the only ones I still have are my bala's (which I love BTW), and gourami's. That is why I was so worried about the person getting bala, I lost 4 fish in the begining (2 to death and 2 to new homes) and I know how terrible I felt.
To correct myself it does say they grow up to 14" not 18", and actually should be kept in groups of 6 not 3.
To answer what makes good tank mates, my dwarf gouramis go great with them...but I would say unless you DO plan on going bigger with the tank steer away from the bala.
Just my opiniom,
Gin