I feed mine 'New Life Spectrum - community fish formula sinking 1mm pellets' and my clowns love it. For whatever reason mine won't go to the surface to eat so whatever I feed them has to sink. Supposedly with New Life Spectrum food you don't really have to vary their diet because the food already has so much different good stuff in it. I've fed them strictly that and haven't had any problems. It is also great for bringing out color in your fish and keeping it! I can vouch for that. http://nlsfishfood.com
Also once or twice a week I feed them a few slices of cucumber overnight