High quality ingredients, several formulations for carnivores, herbivores and omnivores. Specialty foods for breeding fish, raising fry.
He also sells freeze dried foods.
Any of the frozen foods are good. They're typically the most nutrious. Look for frozen with two ingredients: the frozen animal and moisture (water). I feed a little frozen brine and mysis shrimp, bloodworms, plankton and krill.
Sometimes, I'll feed a dry, shrimp or algae pellet and some minced garlic.
Fish don't need much. I feed a little, two times a week. That way, the fish are always foraging around the tank looking for a small leftover. The fish stay healthier, there are no problems with algae and my tank water stays crystal clear.