Aquarium Fish Nutrition

An overview of the nutrients fish require, including protein, lipids, carbohydrates, vitamins, and minerals, and how needs differ between carnivores and herbivores.

Essential nutrients

The nutrients essential to fish are the same broad categories required by most other animals: water, proteins (amino acids), lipids (fats, oils, and fatty acids), carbohydrates (sugars and starch), vitamins, and minerals. Pigments such as carotenoids are sometimes added to enhance coloration.

Protein

Protein is the largest dietary component for most fish. According to University of Florida IFAS data, prepared diets typically contain 32 to 45 percent protein on a dry-diet basis, and must supply ten essential amino acids: lysine, phenylalanine, arginine, valine, leucine, isoleucine, methionine, threonine, tryptophan, and histidine. Diets for fry and fingerlings frequently exceed 50 percent crude protein, grow-out diets often approach or exceed 40 percent, and maintenance diets may contain as little as 25 to 35 percent.

Lipids and fatty acids

Lipids provide concentrated energy and supply essential fatty acids. IFAS lists a dietary fat range of about 4 to 28 percent, with at least 1 to 2 percent consisting of essential fatty acids. Many fish require long-chain fatty acids (C20 and C22) that are not found in tissue from terrestrial plants or animals, which is one reason fish meal and fish-derived ingredients are common in feeds.

Carbohydrates and fibre

Carbohydrates make up roughly 10 to 30 percent of typical prepared diets. Cooked carbohydrates are a relatively inexpensive energy source that can spare protein from being used for energy, which matters because protein is otherwise the most costly part of a diet. Indigestible fibre, such as the exoskeletons of crustaceans, is not generally digested and instead contributes roughage that supports the movement of food through the gut.

Vitamins and minerals

Vitamins and minerals each account for roughly 1.0 to 2.5 percent of a prepared diet. Most fish require dietary ascorbic acid (vitamin C), and vitamins A, D, E, and the B complex are routinely added to fish foods. Stabilized, phosphorylated forms of vitamin C are used because they store better.

Carnivores versus herbivores

Fish are classified by their natural diet as carnivorous (primarily animal material), herbivorous (primarily plant and algae material), or omnivorous (both). These classifications guide the choice of formulated foods, with carnivore, omnivore, and herbivore formulations available to match a species' natural feeding habits.