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Tilapia: Tilapia (usually Oreochromis niloticus or the Nile tilapia) are the most cultured fish in aquaponic systems. They are tolerant of both crowding and relatively poor water quality conditions. They do best at water temperatures of 25-30°C. At temperatures < 24°C, their growth slows substantially, and they become susceptible to disease. They breed readily and abundantly. In fact, if using mixed sex fish, unintended spawning in the system can be a problem particularly in DWC beds where tilapia will consume all available plant roots. Monosex fish (all male) are available and preferred. Tilapia are widely accepted in the marketplace. If available, ethnic markets, which accept live or whole fish, should be considered. The tilapia is most efficient when grown to ¾-1 lb. in final weight. For processed products, such as fillets, tilapia must be raised to large sizes since they have low fillet yields (33% of body weight) compared to other species.
Producers who choose to culture tilapia can be in competition with imported frozen product or with large domestic recycle systems, which drives down market price.
Common carp or Koi: The common carp and the Koi are the same species (Cyprinus carpio). The Koi is just a colorful genetic strain. Although widely consumed in other parts of the world, there is no food fish market for carp in the U.S. Carp are very hardy, have a wide temperature tolerance, and tolerate crowding and poor water quality. Fingerlings for stocking are usually readily available. They can be marketed as ornamentals, fetching high prices per fish. For systems that primarily use the fish as a source of organic nutrients, Koi can be a good choice because of their hardiness.
Channel catfish: The channel catfish (Ictalurus punctatus) is a major aquaculture production species in the southern U.S. It is widely accepted in the marketplace but brings a relatively low sale price, resulting in low profit potential. Ethnic consumers may pay higher prices for whole, quality catfish. Although a good pond culture species, the channel catfish is not as hardy as some people assume. In tanks they can be aggressive, and injury during feeding may occur from barbs located on the head of the fish. At water temperatures between 20-28°C, catfish are susceptible to a bacterial disease known as ESC (Enteric Septicemia of Catfish).
Largemouth bass: Largemouth bass (LMB, Micropterus salmoides) have become a relatively popular culture species. They bring high selling prices, as they have markets as both food fish and recreational stocking.
Bass will not readily accept artificial feeds as small fingerlings so producers must buy fish that have been feed trained. So far, LMB growth in tanks is much slower than for fish grown in ponds (Watts et al. 2016). Lack of domestication and confinement to the high-density environment of tanks contributes to additional time to harvest for tank-cultured LMB. LMB fingerlings are available most of the year from sportfish suppliers but the price differential is large. For example, in April or May, the price for a 2-3 inch fingerling is >\$1.25 USD per fish, but in June they are \$0.30-0.40 USD per fish. Two-inch feed-trained fingerlings are generally available in early June from suppliers in Arkansas and Alabama and 6-8" fingerlings are available in the late fall (usually November).
Rainbow trout: The rainbow trout has the longest history of culture of all the fish considered here. While the others are warm water species, the trout is a cold-water species with optimal temperatures of 14-16°C. Because they evolved in cold-water environments, they need high levels of dissolved oxygen and have little tolerance for poor water quality. Trout fingerlings are available in certain areas of the U.S. (Idaho and North Carolina) but are not always available in small numbers. If conditions are properly maintained, trout grow rapidly and are well received by consumers. Trout require a high protein feed, with a minimum of 45% for juveniles and adults. Trout production for small-scale producers is challenging due to the high cost of feed and competition with commercial markets.
Barramundi: The barramundi is a native of Southeast Asia and into Australia. Like the tilapia, it has been successfully raised in different production systems. It is often sold in restaurants and markets as Asian Sea Bass. It grows rapidly and produces a product that is well received. However, at present, there is no source of fingerlings in the U.S.
Source: Janelle Hager, Leigh Ann Bright, Josh Dusci, James Tidwell. 2021. Kentucky State University. Aquaponics Production Manual: A Practical Handbook for Growers.