What other things can i feed my jack dempsey and oscar?

My 2 fish are both 2" each, are in a 30 gallon tank and i will put them in 500 gallon when bigger with the arowanas, alligator gars, and cichlids. But i just want to know what other things do you feed your jack dempseys and oscars besides pellets and prepared fish food and when should i start feeding rosy reds to oscar and jack dempsey. or how big should they be.