Feeder fish
Small, inexpensive fish used as live food for captive predators.
Feeder fish is the common name for certain types of small, inexpensive fish commonly fed as live food to other captive animals such as predatory fishes, carnivorous aquarium fish, turtles, crocodilians, and other piscivores. The species sold as feeder fish are invariably some of the easiest fish for fishkeepers to rear and breed, such as common goldfish, guppies, and fathead minnow, and are tolerant of overcrowding with high fecundity and rapid growth rate.
- Common species
- common goldfish, guppies, fathead minnow, rosy red minnows, mosquito fish, platies, female Siamese fighting fish, young tilapia
- Primary drawback
- contamination with bacteria and parasites, including skin and gill lice, parasitic intestinal worms, neonatal tetra illness, whitespot, velvet
- Nutritional risk
- thiaminase enzyme destroys thiamine (vitamin B1), causing thiamine deficiency linked to neurological disorders, early life-stage death, crippling morbidities
- Regional opinion
- common in the United States; much less commonplace in the United Kingdom, where aquarists generally reject use as unnecessary and likely to cause health problems
Lore & Background
Feeder fish are typically reared extensively, exposing them to various pathogens, and are often kept in overcrowded conditions. This makes them a vector for diseases such as whitespot and velvet, which spread easily among feeder fish. Some species used as feeders, like goldfish and rosy red minnows, contain high quantities of thiaminase, an enzyme that destroys thiamine, leading to nutritional imbalances in predators. Thiamine deficiency has been associated with early life-stage death, neurological issues, and significant population losses of predatory fish. The use of feeder fish is fairly common in the United States, but in the United Kingdom it is much less commonplace, with hobby magazines generally rejecting the practice as unnecessary and likely to cause health problems.
Reader's Guide
Feeder fish hold significance in fishkeeping as an affordable and readily available live food source for predatory animals, including aquarium sharks, oscars, gar, grouper, rays, turtles, and crocodilians. Their ease of breeding and tolerance of overcrowding make them economical for farmers and hobbyists. However, the practice carries notable drawbacks: feeder fish often carry bacteria, parasites, and viruses due to extensive rearing, and some species contain thiaminase, which can cause thiamine deficiency in predators, leading to neurological disorders and mortality. Many predatory species can be weaned onto dead alternatives. The hobby is divided regionally, with the United States seeing common use while the United Kingdom largely rejects feeder fish as unnecessary and risky. The legacy of feeder fish is thus one of convenience versus potential health risks, with ongoing debate about their nutritional adequacy and disease transmission.
Did You Know?
- Feeder fish are commonly fed to aquarium sharks, farmed salmon, tuna, oscars, gar, grouper, rays, turtles, crocodilians, and zoo animals such as grizzlies, water snakes, cetaceans, pinnipeds, and penguins.
- Thiamine deficiency from feeder fish has been linked to early life-stage death, neurological issues, and significant population losses of predatory fish.
- In the United Kingdom, feeder fish use is much less commonplace than in the United States, with hobby magazines generally rejecting the practice.
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