You could use an algal wafer or pellet, or even a spirluana flake, however its not an essential requirement for good looking platies. I have found that they take great interest in these foods when target feeding another species . Personally I reckon that the nutrafin livebearer flake is pretty well perfect for regular diet, the freeze dried tubifex and the flake provide a good combination for great colouration. As a treat I reckon vegetables or plant material, and as a special treat brine shrimp dont go astray.