Second time I see a school. Looks great!
FWIW, Arapaimag (Michael Bryce) says this is the nastiest fish out of all he has kept. I got one for the first time about half a year ago from Rapps. Grew from 4" to ~10" in 240 gal with all other outlaws - purple labeo, black sharks, Prochilodus lineatus, and Asian USD catfish, and just went into a 4500 gal. We'll see.
My schools been going strong for the last one year, started with 6 @ 2.5" size, now they 8-10", but lost one to my oversight, it got wedged in a hollow driftwood, and got injured, I moved him into a tank, with not so good a cover.
Nasty, would be one other way to put it, I find them extremely energetic and hungry at most times, most of their energy, can be put to good use, by adding a water jet in the tank.
Keeping them well fed is another good option, because once they get hungry, they go berserk.
I have seen them rip out chunks of wood, from the tank hood.