First thing that came to my mind is a warmouth. No, it's not a cichlid. However, is gets a more robust body shape than the cichlids that would stay smaller. Also, they have a big appetite and a big mouth to match. On top of that, where they are native, you wouldn't need a heater and if you enjoy fishing you could very easily get one for free. I use to have one that would eat shrimp, pellets, feeder minnows, or anything else I dropped into the tank. He was very enjoyable. Sorry if it isn't what you're looking for. i just thought I'd make the suggestion.