Live food is the feeding of food which is alive. This includes small microscopic organisms such as infusoria, brine shrimp, nitrosomonas, etc.
Fish are always consuming live food in the aquarium in the form of algae and microscopic organisms which grow in rocks and on the glass walls of the aquarium. However, many aquarists prefer to add live food as part of the main feeding.
Common live food include worms, microscopic plants like daphnea and infusoria. Some even resort to the controversial practice of feeding other fish such as gold fish and guppies as food.
Even common insects such as mosquito larvae, houseflies, earthworms and ants are used as food for fish.
Live food is free of preservatives and other processing chemicals.
Many aquarists culture their own live food. Worms and other microscopic foods such as infusoria, daphnea can be cultured at home. Earthworms can be cultured at home too.