Well I inherited two bala sharks for my 220, one is 8 inches the other is 10 inches. After watch them for a bit it was clear that the wolf fish was stalking them even though the bala is the same size as the wolf and the other is bigger. So during the night I think he would've attacked them and possibly killed one. So I decided to pull out the Wolf and give him a 55 of his own for the time being. Now the sun cat, tire track eel and polypterus endlicheri don't bother them. I like the activity they add to the tank, was thinking of trying to find another one to make it three total. What else is a good fish that will work with the bala's?