Multiple America - legal arowanas?

Afaro juvies seem to relish in killing each other. However, once past the juvie stage they tend to ignore each other. I've been able to re-comm afaros with no aggression issues at the 1-year mark. Leis have the least amount of aggression in my experience. Sub-adults may present towards each other (mouth open lunge) but, I've never seen contact or signs of actual damage (no missing barbels or split fins).
Mixing species is another matter. My afaros showed aggression towards conspecifics until their 1st year.
Why singles of each species? How about a small group of black aro? Once a couple pair off, remove the rest and see if you can get a bonded pair to spawn. I did that with a group of silvers and the bonded pair spawned for me in a 300gal.

Hmmm,...pointers,... are you looking for things like bulking up juvie S. Am. aros on baby crickets? Providing aros with surface cover until they're around 10"+ to provide for juvies increased survival instincts (adult fish outgrow a large number of their natural predators)?

I conditioned my adult silvers on large crickets, shiners, and sticks with occassional feedings of earthworms, grubs (as available from my compost piles), anoles lizards, and small grass frogs. The tank had a shallow substrate of fine pea gravel and nothing else except for a clump of dwarf papayrus plants growing in one corner of their 300 gal. My aros were used to movement and people since their tank was next to my cash register counter in my hatchery in WA. Their W/D was a home-built from a 125gal tank and the water return was water-fall instead of a solid stream. In late winter/early spring, once the female looked heavy, I'd do a 30% water change with water that was a few degrees cooler then their normal temp. Both times they spawned was during the night after the water change (a few blue lights would be left on at night. All indoor white lights would be out). The fry were stripped once the eggs hatched and raised in a stock bin I plumbed into the adult's tank filter loop. I stripped the young because the adults would not feed while their buccal sacs were full.