1 - 1.5 mm pellets are my primary food. They have the same food value as flakes, however, It is easier to measure the pellets to manage quantity fed, which I like to do. For example, 1 teaspoon of pellets weighs 3.1 grams. 1 teaspoon of flakes weighs 0.8 grams ( unless you pulverize them). My fish are voracious. Consume all of them before they make it to the bottom of the tank.
I think natural food - shrimp, fish,clams, etc would probably be better, but I'm lazy and it is so much easier to deal with pre-processed food.
I occasionally feed frozen brine or mystsis shrimp cubes, but as a treat since they are primarily fropzen water with a much lower nutritional value gram for gram than pellets or flakes.