In a 5,000-gallon fish tank in a 1980s greenhouse off a side street near Fred Jackson Boulevard, about a thousand koi fish, the fish so often found in Japanese garden ponds, are busy growing lettuce.
The “tank” is actually an uncovered, blue-tiled, above-ground swimming pool that local organic farmer Pilar Reber purchased at Target about nine months ago. To see the fish clearly, though, you have to walk on tip-toe to the pool’s edge because the koi are, well, coy. They sense the vibrations when a person walks toward the pool, and they dive from the surface on approach.
“They’re pretty shy — they used to be more friendly when they were younger,” Reber said.
The foot-long fish, which Reber ordered from farms in Florida and Barstow, Calif. when they were just about an inch long, exhale ammonia — it’s their waste product. Then, bacteria that Reber has grown in the koi fish tank convert that ammonia into nitrate. And nitrate is a lettuce fertilizer.
“You’re building an ecosystem, and everything has to be in balance, and once you’ve got the balance, you’ve got lettuce cranking,” Reber said. She calls it, for now, guppyponics. (The scientific term is aquaponics.)
The water in the fish tank, with the bacteria converting the fish ammonia into nitrate, is funneled into a 4,000-square-foot lettuce bed, the roots of the lettuce covered and under water absorbing the nitrate. The water, then free of the nitrate — which would be fatal to the fish in high amounts — is returned, clean, to the fish tank, and the process begins again. Reber said the aquaponics system uses 90 percent less water than growing lettuce in a field.
Reber, who owns the Sunnyside Organic Seedlings farm in Richmond, has sold only about $400 of the fish-grown lettuce so far, but she said it’s taken eight months to let the fish-bacteria-lettuce ecosystem develop (the bacteria has had to grow), and she said she expects to harvest about 1,500 heads of lettuce weekly when the system is mature.
This first system will serve Reber as a demonstration, which she plans to use to apply for funding for another aquaponics greenhouse she intends to be five times the size of the current one.
Reber is passionate about organic farming — she began her career as a pesticide applicator but started an organic farm in 2004 after two of the pesticide applicators on the non-organic farm where she was working in the Salinas Valley bore children with corneal blindness. But Reber said she saw marketing potential in her aquaponics system.
“You can’t go anywhere in San Francisco [now] and not get an organic lettuce salad,” Reber said. “And so now chefs are saying, ‘What’s next?’ They’re saying, ‘We want local, and we want biodynamic.’ And biodynamic is a closed system. It means your inputs are from your farm. … You’re producing your fertilizer and your food in one place.”
According to Donald Bailey, a research specialist and the acting program leader of the aquaculture program at the University of the Virgin Islands, which has been researching and developing aquaponics systems for the past 30 years, aquaponics carries high startup costs.
Bailey said the infrastructure — the tanks, plumbing and pumps — is expensive, but that the investment can pay off in the long run if you have a good business plan.
Bailey said he believes aquaponics will become more common as petroleum becomes a limited resource, because inorganic nitrogen fertilizers are petroleum-based.
“Nitrogen’s an abundant resource right now, but it’s going to become limited, and we are maximizing the recovery of nitrogen [with aquaponics],” Bailey said.
Reber said she intends, eventually, to even use recycled fish food. She works in partnership with the Bay Area Rescue Mission, whose culinary students sometimes come to work on her farm — and she has an idea to use food scraps from the Rescue Mission to harvest soldier fly larvae the koi fish can eat.
She thinks it’s the future of urban agriculture.
“If we want to have green belts around our urban areas, this has got to be part of it,” Reber said. “It’s a way to do small gardening but heavy production without depleting your soil or your environment.”
Monty Dusley, the Sunnyside Organic Seedlings farm manager, said he’s excited about the prospects.
“Once we can get it to maintain itself, it’s totally hands-off,” Dusley said. “All we’re doing is transplanting the lettuce into the farm and taking it out. Who would have thought fish can do this?”