A fish can obtain a good deal of nutritional value from a natural live food. Some fish are carnivores and benefit from hunting and catching this type of food. Live foods are excellent for bringing fish into breeding condition. The movement of the live food will also encourage finicky, new, or sick fish to eat. Be careful in feeding insects to your fish without proper research.
Some insects are actually poisonous to fish.
Mealworms can be fed to certain varieties such as the African Butterflies. Nightcrawlers and red wiggler worms can be fed to larger varieties of fish. These are great if you plan to be away from home for several days. They are usually in tablet form, or can come as food packed into a mold that is designed to dissolve slowly over several days, releasing food into the water. Dispenser feeders can also be purchased that automatically release food at regular intervals.