AquariumStocking

How Much to Feed Tropical Fish

Published October 3, 2026. Built by Jeremy Panasuk.

Quick answer: University of Florida IFAS document VM114 says maintenance feeding of 0.5–1.0% of body weight per day is adequate, fish should probably be fed at least 5 days a week, and one feeding per day is plenty for most pet animals. The most common pet-owner mistake in that paper is over-feeding, often with degraded water quality. This page does not convert that percent into grams, because it has no sourced body weight for a neon, a tetra, or any other named pet.

The pet-tropical schedule

VM114 is Ruth Francis-Floyd's extension paper, original publication March 2002, reviewed October 2011. It is written for fisheries and aquarium nutrition, and it is frank that ornamental diets are not as thoroughly studied as channel catfish, salmonid, and tilapia diets. For other species, including freshwater and marine ornamentals, nutritional management in that paper is a mix of those production data and the experience of successful aquarists.

Fish should be fed as a percentage of body weight. For maintenance, 0.5–1.0% of body weight per day is adequate. Feed at least 5 days per week. One feeding per day is plenty for most pet animals. Young stock are the exception inside the same paragraph: rearing them requires small meals fed more frequently, which commercial farms often do with automatic feeders. A community tank of adult tropical fish is the first schedule. A grow-out of fry is the second. Do not average them into "a pinch three times a day."

Maintenance diets may contain as little as 25–35% crude protein. Grow-out diets in the same paper often approach or exceed 40% crude protein, and foods for fry and fingerlings frequently exceed 50%. Protein comes down as growth slows. Fish meal should remain a major protein source; the paper does not recommend low-cost formulas that drop fish meal for terrestrial proteins such as soy, because fish need amino acids and long-chain fatty acids that those substitutes do not supply.

Flakes are the form most home tanks use. VM114 says the volume required to meet the animals' needs may be deceptively high, and the author recommends weighing the diet so the keeper does not accidentally underfeed. That is the opposite problem from the common one, and both are in the paper: owners usually over-feed, and occasionally they underfeed by enough to matter. Weighing is how you stay near 0.5–1.0% instead of judging a cloud of flakes by eye. Without a body weight from a cited source, this page stops at the percent. It does not invent a gram weight for a species.

Koi and goldfish are not on this schedule

SRAC Publication No. 7201, the September 2004 species profile of koi and goldfish, says goldfish and common carp lack true stomachs, so they benefit from multiple feedings each day. That sentence sits in a production section. Most producers in the same profile use a 25–32% protein diet through grow-out. Multiple feedings are for those fish because of the missing stomach, not a general tropical rule you can carry back to tetras. The pond-side limits are on how many koi in a 500-gallon pond.

Storage, because rancid feed is a feeding error

VM114 says fish feeds should be purchased frequently, ideally at least once a month and more often if possible, stored in a cool dry place, and never kept on hand more than three months. Refrigerating dry feed is not recommended, because that environment is moist. Freezing is an acceptable way to extend shelf life. Feeds without stabilized (phosphorylated) ascorbic acid are not recommended. Ascorbic acid deficiency is the classical cause of scoliosis, or "broken back disease," in that paper. Better manufacturing has made it less common. It is still on the list when a fish's spine bends.

Worked example: over-feeding shows up in the water-change math

The stocking and water-change functions on this site are planning estimates, not a published feeding trial. VM114's link from over-feeding to water quality is the reason to run them. Nothing below is a measured nitrate test from a real tank.

Stocking inputs: 20 gallons, normal setup, 8 small fish. Points are 8. Capacity is round(20 × 1.0) = 20. Percent is round(8 / 20 × 100) = 40, which is comfortable. That load is a cycled-tank plan. It does not tell you how many flakes weigh 0.5% of those eight fish.

Water-change inputs, which are the calculator's example inputs and not a measured week: nitrate rises 20 ppm, ceiling 40 ppm, tap water 5 ppm. The function returns a 60% weekly change and a plateau of about 38 ppm.

The fraction that would hold the plateau at the ceiling is rise / (ceiling − tap) = 20 / (40 − 5) = 20/35. The function rounds that fraction up to a 5% step: ceil((20/35) × 20) × 5 = 60%. The plateau at a 60% change is round(5 + 20 / 0.60) = round(38.333) = 38 ppm. If over-feeding pushes the weekly rise higher than 20 ppm, you re-enter the new rise. This page does not supply that higher rise, because it was not measured here. Run it on the calculator from your own test log.

A second stocking check: 20 small fish in the same 20 gallons are 20 points, 100%, at capacity. The environmental chapter of the Merck Veterinary Manual says beginning aquarists overstock and overfeed, and that the result is ammonia or nitrite spikes. Sitting on the 100% line and feeding past VM114's maintenance percent is that pairing. Feeding should be cut when ammonia is already high; that chapter says feeding should be discontinued or substantially reduced until the ammonia problem is corrected. The new-tank version of the same failure is cloudy water in a new tank.

A common mistake

VM114 names it directly: the most common mistake pet owners make is over-feeding their fish, often degrading water quality. A pinch at every pass by the tank is not the one-feeding-per-day schedule. The flake pile looks small because the food is airy. Weigh it, or accept that you do not know whether you are near 0.5–1.0% of body weight.

Limits, and when to call a veterinarian

Nutritional disease, in VM114, is often a diagnosis of exclusion. Starvation can follow a keeper cutting feed to chase a water-quality problem until the fish are in negative balance. Scoliosis can be ascorbic acid deficiency, and nutritional gill disease from pantothenic acid deficiency is described in channel catfish in that paper. None of those are things to decide from a feeding chart. If fish are losing weight, bending, or wasting while you are already at one small weighed feeding, an aquatic veterinarian should see them. Young fish on a grow-out schedule are outside this maintenance note. So are koi and goldfish.

Adding the fish that will eat this food is how to add fish. The full starter order is how to keep pet fish alive.

Shop a digital gram scale on Amazon

Affiliate Affiliate disclosure: as an Amazon Associate, we earn from qualifying purchases — at no cost to you. A scale is listed because VM114 tells the reader to weigh the diet. This site has not tested a scale.

Compiled with AI assistance from the sources below. Spot an error? Email jpanasuk@gmail.com.

Sources