Few years back i raised a buterkoferi. I had him in a 20 gal tank with 2 oscars

. all three were raised from couple inches for few years. oscars got up to about 8 1/2 inches or so and the butter smaller at about 7. Even though the oscars were bigger than the butter, the butter was pretty much the boss of the tank. I would witness the butter chasing the oscars around the tank and bullying his two larger tank mates. Amazing fish but aggresive. i would feed them lizards and geckos often, and the butter would try to steal the lizard/ gekcos from the oscars mouth

. having a school of these would probably be very cool. i debated on getting a few to put with my current oscars in my 100gal but decided against it, remembering fish fights at 3am, water splashing and such...
My LFS says the sale of these fish is now illegal (but they still have some for sale lol) due to the fact that after time people get rid of them in lakes or rivers and what not, and the butters are taking over fish poplulations in different places. being a very hardy fish, not much can be done to control/lessen popolation of butters; not sure how accurate that info is but sounds reasonable.