I love your aquarium. Big cichlids are impressive.
I had an eight-foot long, 300-gal. Central American cichlid tank years ago - big Blackbelts, Chocolate cichlids, Red devils, Salvini, etc. - lot of Heros & Theraps spp. (We called them all Cichlasoma). Lots of spawning and fighting. They locked jaws, sometimes fought like pit bulls.
It was cool. Until the left side of the tank came loose. 300 gallons on the floor and out the back door.
Ever considered any Leporinus species?