Fish do not need to eat much. It is very important to understand that overfeeding may cause sickness or death to your entire biological community. More food also means more organic waste that makes the tank polluted.
What to Feed Your Fish
Similar to all other living things, fish require variety in their diet. The dried variety of fish food available in the market is sufficiently nutritious. The dried food should be combined with fresh, green, live and frozen food.
Green Food: The fish should periodically be fed leafy greens, zucchini, spinach, and fresh peas, all which should be finely chopped and reduced to consumable size for the fish.
Live Food: Treat your fish occasionally with earthworms, brine shrimp, and midge larvae. Even though the fish love it, this food should not be fed frequently!
Frozen Food: Small bits of frozen seafood such as fish, shrimp, crab, and roe, are great for the fish. Aquarium dealers often stock aquarium-specific frozen foods such as bloodworms and mealworms. Defrost this food in a cup of tank water before feeding it to your fish. The food should thaw in about 5-10 minutes, depending on its size. Rinse the food with a little more tank water, and then chop it up a little more before you place it in the tank.
When to Feed Your Fish
As is true with all animals, different types of fish have different feeding habits. The carnivorous fish feed about twice a week, while the herbivorous feed on a daily basis. Keep this in mind when you buy your fish. Normally one small meal per day is what an average fish requires to live well, provided you have placed live rock in the aquarium and that there is a good supply of algae.