A varied diet will maximize the health of your Siamese fighting fish.
You should offer high quality specialised Siamese fighting fish pellets/granules and supplement this with black worms, brine shrimp, frozen tubifex worms and daphnia.
Siamese fighting fish should be fed 1-2 times per day in very small amounts (2-3 pellets or pieces of other food). You should ensure all foods aside from pellets are broken into tiny pieces before feeding.