We had some fishy visitors on our farm this summer. New Haven's Sound School needed a place to keep its classroom tilapia over the summer vacation. I've been interested in this tropical fish, which is raised for food in many parts of the world, ever since I saw the elegant, solar-powered, fish-and-vegetable-producing greenhouses the New Alchemy Institute created on Cape Cod decades ago. Now this delicious white fish is showing up on the menus of some of the best restaurants.
Our farm had a good, sunny site for a pond for these warm-water fish. Several mornings last spring students from the vocational aquaculture program came out with Neil, their teacher, and some shovels. Together, we dug a twenty-foot-by-twelve-foot pond about four feet deep. Even the bus drivers helped. Fortunately, the subsoil was mostly sand, so the digging was very easy.
One large roll of polyethylene provided three layers of waterproofing. We filled the pond a little at a time with water from our well, aided by some of this spring's copious rains. In late June, when school ended, Neil brought buckets of fish to the pond.
The tilapia quickly adapted to their new environment. They like to eat algae, so the normal tendency for a pond to grow this green plant is useful. The pond also attracted a lot of frogs and beautiful insects.
About four months later, the tilapia were ready to harvest. After school, Neil brought several students with buckets and nets to our farm. I'd already siphoned out much of the pond's water. The biggest fish get eaten. The others returned to the Sound School's campus on New Haven's harbor for classroom projects.
We learned some valuable lessons. Next year, we'll add a filtering mechanism and perhaps a clear covering to boost the water temperature with the sun's help. Both of these improvements should increase productivity.
As Suzanne and I have read more about the overharvesting of the world's fisheries and widespread pollution problems (including PCBs in the Housatonic and excess nitrogen in Long Island Sound) we've eaten fish much less often. However, fish provide such an excellent source of high quality protein, it's exciting to be learning, along with high school students, how to raise, on an appropriate scale, tilapia for food.
On the Old Solar Farm,
This is Bill Duesing, Living on the Earth
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