If demand for fish is low in your area and competition from imported products is high, consider skipping the edible varieties and sticking to ornamental fish. Most ornamental varieties are tropical in origin, so you’ll definitely need heated water if you’re in a temperate or cool area.

Goldfish

Finding a contract with a national level aquarium and feeder fish supplier could make goldfish the perfect profit machine for your aquaponics system. With some supplemental heat and minimal aeration, goldfish are happy to reproduce and grow to surprising size with a minimal amount of basic pelleted feed. Even if a particular type of fancy goldfish might take six to 12 months to mature to the desired size, the low-maintenance requirements of the species make it worth the wait. There’s also a need to process the fish or freeze them according to food safety standards, speeding up delivery when it comes time to transfer them to the buyer.

Koi

While koi are larger and slightly hardier than their smaller goldfish cousins, they actually require more care and attention due to greater sensitivities to water conditions. Koi can handle slightly cooler temperatures at 65 to 75 degrees F, while goldfish generally need 70 degrees and up. Some cultures consider them edible, but they fetch higher prices when grown to large size for pond and aquarium display. The omnivorous diet simplifies feeding, but you’ll need plenty of dissolved oxygen and tightly controlled ammonia levels to keep them growing to the sizes that fetch the highest prices. It can also take years to grow a koi that demands a collector’s attention.