Good question. From the info. I've gathered, frozen foods are the most nutritious. I feed brine and Mysis shrimp, plankton, krill and bloodworms. There are no additives, so nothing that would be difficult for the fish to digest. Additives, for the most part, just extend the shelf life of a product. Flaked foods typically have high phosphates, not good if the fish don't eat all of it and the leftovers create algae problems.
Garlic is very good for fish. I feed minced garlic sometimes. It's natural antibiotic properties boost the fishes' immune system.
"Fear not, my young apprentice. Just change the tank water."