if you want to do 1 each I would just do 1 terror and 1 severum. That's 2 8 to 10" fish and maybe a school of congo tetras or danios. I error on the cautious side. I have 3 fish right now and 3 55 gallon tanks no tank mates. I think Rivers would be more help on the terror as he keeps one. Im just not sure on the bio load on them.