How Much and How Often to Feed Aquarium Fish

Learn how much and how often to feed aquarium fish: the 'only what they eat in a couple of minutes' rule, evidence-based rations as a percentage of body weight, small frequent meals, and why overfeeding wrecks water quality by raising ammonia.

The most common feeding mistake is giving too much. A simple practical rule used by experienced fishkeepers is to offer only as much food as the fish finish in a minute or two, then stop. Underfeeding is far safer than overfeeding, because any food that is not eaten sinks, decays and pollutes the tank.

How much to feed

Veterinary and aquaculture guidance expresses rations as a percentage of body weight per day. Maintenance rations are small, on the order of 0.5-2% of body weight per day, while actively growing fish and grow-out diets are fed at roughly 3-5% of body weight per day, and fry and fingerlings up to about 5% (UF/IFAS; Merck Veterinary Manual). More food does not mean proportionally more growth: in tilapia feeding trials, growth increased about four-fold when the ration rose from 1% to 2% of body weight per day, but raising it further to 3% added only a small amount (FAO). Beyond a point, extra food is simply wasted. Several factors change how much a fish needs:

• Temperature: fish eat more in warm water and much less when it is cold, because cold slows their metabolism.
• Age and size: fry and juveniles need proportionally more food (up to about 5% of body weight per day) than settled adults.
• Feeding type: large carnivores take big, infrequent meals, while grazers eat little and often.
• Maintenance vs growth: an established adult needs far less than growing stock.

How often to feed

Most aquarium fish do well on one or two small feedings a day. UF/IFAS notes that for adult pet fish one feeding per day is plenty, and that maintenance feeding at least five days per week is adequate. Fry and young stock need small meals more frequently. Large predatory fish that swallow big meals may be fed only every couple of days. Spreading the daily ration over several tiny feedings, rather than one large one, helps reduce uneaten waste.

Sources: www.merckvetmanual.com , www.merckvetmanual.com , ask.ifas.ufl.edu , www.fao.org