Fish food

Aquarium fish feed is plant or animal material intended for consumption by pet fish kept in aquariums or ponds. Fish foods normally contain macro nutrients, trace elements and vitamins necessary to keep captive fish in good health. Approximately 80% of fishkeeping hobbyists feed their fish exclusively prepared foods that most commonly are produced in flake, pellet or tablet form. Pelleted forms, some of which sink rapidly, are often used for larger fish or bottom feeding species such as loaches or catfish. Some fish foods also contain additives such as sex hormones or beta carotene to artificially enhance the color of ornamental fish.

Prepared foods are those foods that are non-living and are made by the aquarist or bought already prepared for consumption for fish.

Flake food is a type of proprietary or artificially manufactured fish food consumed by a wide variety of tropical and saltwater fish and invertebrates. It is ideally suited to top dwellers and mid-water fish though numerous bottom dwelling species consume flake food once it has settled on the bottom. Flake food is baked to remove moisture, ensuring a longer shelf life. Generally the more moisture a particular example of fish food contains, the more readily it will deteriorate in quality.

Dry foods are also available as pellets, sticks, tablets, , and wafers, manufactured to float or sink, depending on the species they are designed to feed.

Vacation foods, also known as "food blocks" (or "weekend blocks" for smaller versions), are designed to be placed inside the aquarium to forgo feeding while the owner is absent. These blocks release small amounts of food as they dissolve. Food blocks can be a good choice for smaller tropical fish, but can pollute the water if the tank is neglected for too long.

...
Wikipedia