I would scale back to two oscars, and add in a pair of tinfoil barbs, and a blue jack dempsey. I love those blue boys LOL. I have kept tinfoil barbs and oscars, they look good and are active swimmers. I agree that the oscars are super messy, get a good clean up crew for the substrate, a catfish that gets big and a algae eater like a common pleco. Do weekly water changes where you vacume the substrate, dont over feed. You said your tank is 72 inches ? thats six foot, so that is good, its more important to have a longer tank than a higher one, length to cruise is good. If you dont like those suggestions i would go with 2 oscars, 2 slightly smaller(5-7 inches) semi aggrssive new world cichlids, a catfish, and a pleco.
