Thanks again!
Ohkay so I should've clarified that the flatheads eating all the other fish was fine, because the flats got to be "big." And when we moved here, I started feeding them and the bass/bluegill/crappie started flourishing again.
That's why I was initially thinking I would restock the flatheads. But then I started doing some research and thought it would be super cool if I could raise a Nessie (the big 5ft flathead) replacement, and the arapaima was my first thought. I looked at some others, and maybe a Beluga or white sturgeon would be much better? Or is it not cold enough you think? I don't have enough money to go with all those fish, and I'm a bit scared as they might eat other/the bass in the pond already might. I'm deffinitely going to get some logs and try to make a small pond for frogs! ^_^ A beluga would be more than a "worthy" Nessie replacement as it grows, I'm sure. But Idk... I may just be dreaming =P