Want Sustainable Fish? Barn-Raised
Aquaponics takes advantage of nature’s processes to fill Americans’ growing appetite for fish—without overfishing or destructive farming.
Click here to subscribe to YES! Magazine.
At E&T Farms in Cape Cod, Mass., owner Ed Osmun is in the barn, spraying a mixture of cayenne pepper and garlic onto a lush crop of salad greens. The simple homemade pesticide deters aphids but is harmless to other living things. That’s especially important because these greens are growing in water that is circulated to fish tanks full of koi and tilapia. Osmun sells the tilapia at local farmers markets and supplies the koi to garden stores, where they’re sold to populate ornamental water features.
There’s no place for chemical pesticides and fertilizers in this aquaponic system. It’s a combination of aquaculture (cultivating fish) and hydroponics (growing plants in water) that can yield large amounts of protein and produce from a relatively small space, while emitting virtually no waste products.
Aquaponics takes advantage of nature’s process of breaking down waste into life-sustaining nutrients. Bacteria in the tanks convert the ammonia in fish waste into nitrate, a plant nutrient. The water is pumped from the fish tanks through the plant trays, where the plants absorb the nitrate and purify the water before it returns to the tanks. Round and round the water circulates, with plants and fish each serving the needs of the other.
Aquaponics is so efficient that Osmun reports his system has been running for six years without changing the water, only adding some on occasion to compensate for evaporation. The only regular inputs into the system are the fish (purchased as tiny fry), fish food, seeds, beneficial insects for pest control, and electricity. Electricity is the largest input, as a considerable amount of it is required to run the pumps and turn the large waterwheels that oxygenate the water in the fish tanks and spread beneficial bacteria in the water. Osmun uses food pellets to sustain the fish, but some aquaponic pioneers like Will Allen of Growing Power and Robert Olivier of CompostMania are making their own fish food—fly grubs raised on food scraps.
The symbiotic relationship between fish and plants can be harnessed to fill a big human need. Americans now eat four times as much fish as ten years ago—425 million pounds a year. With many wild species threatened by overfishing, and environmental problems caused by offshore fish farms, aquaponics looks like a win-win solution that can spare the earth and sea while feeding humans—almost like nature intended.