My clown fish eat everything, if it is not too big a piece. The best is a variety, including mysis, brime shrimp and spirulina. They also eat flake food. A good quality flake food they like is called PE flakes by piscine energetics.
LRS Fish Frenzy is good, but I find that many pieces are too big for them. They spit them back and the Tang and Rabbit fish eat them instead.