Prepared foods are those foods that are non-living and are made by the aquarist or bought already prepared for consumption for fish.
Dry foods
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, :wikt:granule|granules, and wafers, manufactured to float or sink, depending on the species they are designed to feed.
Vacation food
Vacation foods, also known as "food blocks", 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.
Medicated fishfood
Medicated fishfood is a safe and effective method to deliver medication to fish. One advantage is that medicated food does not contaminate the aquatic environment and also, unlike bath treatments, does not negatively affect fish, filtration and algae growth in the aquarium. The parasites will get treated spot on by medicated food, because the fish is ingesting it.
Freeze-dried and frozen fish diets
Freeze-dried and frozen fish foods were primarily developed for tropical and marine fish and are useful in providing variety to the diet or specialist feeding needs of some species. These include tubifex worms, mosquito larvae, bloodworms, water fleas along with brine shrimp.
Frozen fish food
Perishable food can be preserved by frozen storage, and is often sold in blister packs or resealable packets. These can contain a variety of ingredients such as bloodworms, Daphnia, or brine shrimp, and are commonly used to feed such fish as Discus which require a high protein diet. Often fed on beef heart fish food within the aquaculture industry, the discus fish are not the only fish which can benefit from a high quality prepared frozen mixture such as beef heart, although by far these are the fish most associated with this particular frozen food.
Live foods
Live fish food include earthworms, sludge worms, water fleas, bloodworms, and feeder fish. Food for larvae and young fish include infusoria, newly hatched brine shrimp and microworms. These are the most preferred type of food for fishes, but are difficult to get. However, freeze dried forms of earthworms, tubifex etc. are available now.
Ingredients
Fish food should ideally provide the fish with fat and amino acids and the fish food must be speedily digested in order to prevent buildup of intestinal gas, kidney failure and infections and to avoid aquarium pollution due to excessive ammonia. Aquatic diets for carnivores must contain vegetable matter such as spirulina.
Nutrients
Amino acids are the basic components of proteins. Protein requirements are species-specific. Carnivorous fish need a greater percentage of proteins than herbivorous. An example of an aquatic diet that is a good source of amino acid is a crumbled hard boiled egg offered to small :wikt:fry#Etymology 2|fry. Large amounts of DL-Methionine enhance the headgrowth of the Lionhead goldfish.
Fats that are broken down into fatty acids are the main source of energy in fish especially for the heart and skeletal muscles. Fats also assist in vitamin absorption. Vitamins A, D, E and K are fat-soluble or can only be digested, absorbed, and transported in conjunction with fats.
Carbohydrates are molecular substances that include sugars, starches, gums and celluloses. Most of the carbohydrates that are incorporated into aquatic diets are of plant origin and are sources of the enzyme amylase. Carbohydrates, however, are not a superior energy source for fish over protein or fat but digestible carbohydrates do spare protein for tissue building. Unlike in mammals, glycogen is not a significant storage depot of energy in fish.