Fish aren’t the only non-plant additions to an aquaponics system that can generate the needed nutrients and extra profit. Crustaceans of all kinds can fit into a well-planned aquaponics system; especially the freshwater varieties that tend to stay smaller and reach a harvestable size faster than their saltwater relatives. But don’t assume you can simply add a whole new layer of life to every fish tank simply by tossing crustaceans into the bottom level. Many fish species will happily eat these tank mates, even the hard-shelled varieties, leaving you with nothing to show for your investment. Consider either stocking tanks entirely with crustaceans, or mix them with herbivorous and omnivorous fish species to reduce predation.

Crayfish

Crayfish are the smaller, freshwater relative of the lobster. They are tough and quick-growing crustaceans that can fetch a healthy price per pound whether live or frozen. As long as you don’t overcrowd them and cause cannibalism, they don’t need much dissolved oxygen or perfect pH balance to thrive. They’re a good mix with non-predatory fish because they eat solid waste products and can keep tanks clean. It’s also possible to add them to grow beds rather than just the fish tanks to introduce more life into the overall aquaponics system.

Shrimp and Prawns

Most shrimp and prawn species require saltwater tanks, but some freshwater varieties work well as a part of aquaponics. They require some of the highest water temperatures of all species at 78 to 88 degrees F. Only heated systems and hot tropical climates are appropriate for shrimp culture. However, you need just four months of growth to harvest fair-sized juvenile prawns, so it’s possible to grow just a single shrimp harvest every summer and wait until temperatures return the next year for another run. You’ll need one to two yards of pond or trough space per juvenile prawn to avoid internal predation, so don’t expect a high stocking rate on smaller commercial systems.

Mussels and Oysters

Freshwater shellfish harvested from rivers and lakes tend to have high levels of heavy metals and pollution. Aquaponics offers an ideal alternative for clean production. The hard shells protect these additions from most fish, while the water-cleaning benefits of the mollusks will improve quality throughout the system. Watch out for new mollusks settling in pipes and filter areas where they can create clogs. Be aware that populations can die off suddenly if food levels drop unexpectedly for them due to subtle changes in fish habits or a total harvest.