Freshwater tiger oscar.....?

I have a tiger oscar. For a while we had red-bellied pacu with it and they did fine together, but the pacu got too big even for our 150gallon tank so we gave them away. I am not sure a 55gallon tank will be sufficient for a tiger oscar and other large fish. If it's just the oscar, it should be okay, but if you include other large fish, you will need a much larger tank.