The fish don’t like strangers.
Ellen Perlman pours a scoop of fish food into one of four blue plastic tanks at Chesapeake Aquaponics, about half an hour from Baltimore. Picture a giant kiddie pool that's deep enough to stand in up to your belly.
“You would think we have piranhas here,” she said, expecting a torrent of tilapia to froth the water’s surface but it remains stubbornly smooth. She chuckled. "Maybe not.”
She says the fish recognize her voice and her footsteps, but not a visiting reporter’s.
“Fish are very sensitive animals,” she added.
Environmental sweet spot
But it’s an indelicate aspect of these delicate creatures that makes her garden grow. From these tanks, water rich in what you might call “fish manure” flows through a filter system and into the adjacent plant beds, where lettuce and other vegetable plants float in Styrofoam rafts.
“It’s a way of recycling the fish nutrients,” she says.
It’s called aquaponics. It combines aquaculture - or fish farming - with hydroponics - growing plants without soil.
Aquaponics hits a sweet spot for environmentalists. It recycles fish waste into plant food. Hydroponics typically uses less water than conventional farming. And for those concerned about insecticides on their produce, the fact that the fish share the water with the plants means aquaponic farmers have to be very careful about what they spray.
“Any type of spray would harm the fish,” Perlman said. Even insecticidal soaps popular with organic growers are off limits.
Another part of aquaponics’ appeal is the fact that overfishing is depleting the world’s oceans. Fish farming accounts for at least half the world’s production, but waste from all those confined fish is polluting some areas.
“There are fewer and fewer fish in the ocean and more and more fish will be raised on farms,” said Dave Love, a microbiologist with the Johns Hopkins University Center for a Livable Future (CLF). “The trick is, how do we do that responsibly, sustainably and in ways that make fish farmers money?”
Small but productive
Tackling those questions is what CLF’s Cylburn Aquaponics Farm aims to do.
Located next to greenhouses at Baltimore’s Cylburn Arboretum, the farm has been up and running for a little over a year.
Farm manager Laura Genello says she’s delivering about 10 to 20 pounds (five to 10 kilograms) of produce per week to local farmers markets from about 300 square feet (28 square meters) of growing space.
“Which is relatively small,” she said, “but 10 pounds of greens is a fair amount of greens.”
The farm harvested its first 20 one-kilo fish earlier this fall, and they expect to produce about 275 fish per year.
But whether aquaponics is profitable is an open question. Energy costs are a big factor.
“Our tilapia like 70 degrees (21C). In the winter, it gets quite a bit cooler," Love said. "So, we need to heat the space.”
Cylburn Aquaponics Farm is grant-funded, but Chesapeake Aquaponics is a commercial venture. It has not turned a profit yet, but Perlman is optimistic that providing high-quality fresh greens in the middle of winter will win her a niche market.
The elegance of aquaponics’ symbiosis is alluring, and aquaponic businesses and nonprofit projects are popping up around the country and around the world.
But Genello is cautious.
“I think we have to be careful about not getting ahead of ourselves with the excitement about the system because there are a lot of things that are not quite perfect about it,” Genello said. “That’s why it’s really important for more people to actually do aquaponics, so we get more people experimenting and playing around with what works and what doesn’t.”