Recirculating aquaculture is focused on the production of fish in a controlled environment that is usually separate from natural waterways. Older forms of fish production relied on large nets to section off rivers and lakes to keep fish easy to feed and harvest. The high stocking rates push too much ammonia into the water, resulting in oxygen loss from algae blooms in response to the source of fertilizer. Recirculating aquaculture and aquaponics both solve that problem by keeping the fish out of the waterways and processing the waste in the water to put it to good use as a fertilizer. However, recirculating aquaculture generally doesn't involve growing any plants or crops aside from water plants, like duckweed, that serve as a natural food source for the fish.

Hydroponics vs Recirculating Aquaculture

With no crops involved to harvest and sell, a farmer using recirculating aquaculture must rely solely on the fish, and their by-products, to turn a profit. With Americans eating only 10% as much fish as all other meats, it can be hard to find a market with enough demand for fish to overcome relatively low costs per pound and high competition. Ornamental fish work well in heated greenhouse environments and tropical climates, but there's still a limit to demand for koi and other aquarium and pond fish. You can't simply add rafts of floating plants directly to the ponds and tanks used in recirculating aquaculture either. The direct exposure to unprocessed ammonia, high nitrate levels and solid waste particles can kill the plants or at least stunt their growth.

Most fish tanks are also kept out of the bright and direct lighting that plants require in order to discourage algae growth. Because hydroponics separates the fish from the plants and processes the waste and water in between the two with the help of bacteria and biofilters, it's possible to control the levels of exposure to certain nutrients for optimal growth for both sides. Even with recirculation, aquaculture systems tend to need higher levels of fresh water coming in and more waste water going out than aquaponics. This is because there's no intermediate level of plants to absorb a large percentage of the waste products before filtration is used, resulting in a greater load on the biofilters and mechanical filters used in recirculating aquaculture.

Cross Training in All Three Practices

Training opportunities for hydroponics or recirculating aquaculture programs will still give you a strong foundation for starting an aquaponics business. Techniques for keeping fish healthy or plants growing well in water apply to all three disciplines. You may have to adjust the designs and rates for some aquaponics systems due to the differences in water quality goals, but the basics apply universally. Many areas only offer training in hydroponics and traditional recirculating and non-recirculating aquaculture, as these systems have been in development for longer periods of time. Learning whatever you can locally and combining it with distance and online education specifically in aquaponics will boost your chances of building a successful and profitable business.