I'd wait to see how the aggression level gets when one of the females decides to spawn. The spawning female is the nastiest. She doesn't really give warning blasts or gill flares before she hits the other fish that are too close. The others generally learn pretty fast where to avoid. But your tank is probably big enough to house more pairs of apistos, or more females. For me, the males are not going to focus on killing a female in a 79 gallon planted tank with lots of other fish around-including male apistos-to distract them-and the only thing more females could provide is increased frequency of spawning events in the tank, and potentially more fry. To condition them without fouling the tank too much You can try spot feeding them with a pipette to keep the wasted feed down. Even though they like to feast, those little apistos can't really eat that much. You can also do frequent water changes, that can trigger spawning too.