Angling for a Better Way to Farm Fish--And Vegetables, Too
Aquaponics fertilizes plant crops with bacteria-treated fish waste products. The plants return the favor by filtering the fish's water—and humans can eat both of them
Angling for a Better Way to Farm Fish--And Vegetables, Too
- WASTE NOT: Ferry scoops up a mound of compost containing beneficial earthworms. The relatively small amount of waste generated by the aquaponic greenhouse, be it filtered solids from the tanks, dead fish or wilted plants, is composted and applied to terrestrial crops elsewhere on the farm. John Matson / © Scientific American
- GERM OF THE IDEA: The heart of the aquaponic system is a bacterial bioreactor that converts fish-generated ammonia to plant-friendly nitrate in a two-step process. The plastic "wagon wheels" inside the bioreactor [inset] house colonies of Nitrosomonas and Nitrobacter, the two types of bacteria that process the ammonia. The wagon wheel is designed to maximize surface area and, hence, real estate for the bacterial colonies. John Matson / © Scientific American
- RAFT OF ROOTS: Ferry hoists a polystyrene "raft" of lettuce greens that floats in one of the tubs. The plants are grown hydroponically (without soil) so the roots dangle below the raft and draw nutrients directly from the nitrate-rich water. (Some of the roots are visible below the right edge of the raft in this photograph.) John Matson / © Scientific American
- IN THE LOOP: In these tubs, flooded with water fertilized by fish waste, Cabbage Hill grows high-value food crops such as basil, lettuce and other leafy greens. The roots of the vegetables act as filters, drawing nitrates from the water so that it can be returned to the fish tanks, completing a closed loop. John Matson / © Scientific American
- FOOD FIGHT: A net full of nearly market-size bass is much more volatile than one of fingerlings. Each of these fish weighs about 1.5 pounds (0.68 kilogram) and fights vigorously when caught. Whereas tilapia is the staple fish of aquaponics, more glamorous species like bass are often considered more desirable and can fetch higher prices from restaurant chefs and other customers. John Matson / © Scientific American
- FINNED FARMER: Cabbage Hill's Kevin Ferry lifts young bass from one of the aquaponic tanks. The fish take about 11 months to reach market size from one-inch (2.5-centimeter) fingerlings, during which time they will have fertilized several rounds of vegetable crops. John Matson / © Scientific American
- RISING TO THE OCCASION: Tilapia rise to the surface in one of Cabbage Hill's tanks. A consumer favorite, the hardy species, amenable to high-density living environments, lends itself well to aquaponics. As of 2006, tilapia was the fifth most consumed seafood in the U.S. John Matson / © Scientific American
- MULTITASKERS: In the aquaponic greenhouse at Cabbage Hill Farm in Mount Kisco, N.Y., tankfuls of edible fish serve a dual purpose: They produce thousands of pounds of salable food fish each year which, as they grow to market size, excrete metabolic by-products that are harnessed to fertilize high-value vegetable crops. John Matson / © Scientific American
