DIY





How to Raise Fish for Food at Home

Richard D. Reed shares his experience on how to raise fish at home for the table, including information on brood stock, feeding, water temperatures and purification.

| March/April 1975

Readers of LIFESTYLE! NO. 2 will remember the interview with staff members of New Alchemy Institute East … a Cape Cod research center working to develop more intimate ties between man and the life cycles of organisms that can provide him with food and energy. Out of this search has come a revolutionary proposition: that the average U.S. suburban family can supply all its own animal protein needs by growing fish in a dome-covered 3,000-gallon pool. Tilapia — an African genus-are recommended for this purpose because they can live mainly on algae as adults and don't require constantly running water.

I first met this concept of backyard aquaculture in an article written by New Alchemy's John Todd for Organic Gardening and Farming (November 1971). The idea grabbed me at once. By late 1972 I had cast a ferroconcrete,dome, and spring of 1973 found me finishing the below-ground pool and ordering fish of my own.

Fish Brood Stock

Rather than use the tilapia suppliers suggested by the New Alchemists, I took advantage of a less expensive offer by a local pet shop that ordered from a California source. An investment of $16.00 brought me 16 mature but stunted fish four to four and a half inches long, and 16 young that measured one and a quarter to one and a half inches in length. (I wanted the little fellows to give me an idea of the size I could expect my stock to attain if I got an earlier start in future seasons.) The fish I bought were Tilapia mossambica, one of the three recommended species.

Water Temperatures

By the time the tilapia arrived, it had become clear to me that my underground pool wasn't getting enough benefit from the sun's heat. (The dome is only about 15 percent glass, all on the south side.) The walls of the shelter were too hot to touch and the air in the top registered a steamy 120° Fahrenheit, yet the water temperature remained in the 50's. Since tilapia seem to be happiest in an 80° environment and are threatened by temperatures under 55° Fahrenheit, something obviously had to be done.



Because we have no electricity, I couldn't circulate the water or spray it on the dome's inner walls to warm it … but I still managed to come up with a twofold solution to the temperature problem: [1] I dug all the earth away from the structure's outer south wall to the depth of one foot. This allowed a considerable amount of the sun's heat to be transferred through the one-and-a-half-inch-thick concrete. [2] I then bought 1,000 feet of three-quarter-inch black plastic pipe and spiraled it on bare unshaded ground near the dome. A trickle of water that was run through the coils whenever the sun was out was soon warmed to a temperature higher than that of the pool. A 100-foot length of pipe carried the flow on through the pond, where a large part of the heat was absorbed by the water. (I didn't allow the liquids to mix, for fear of diluting my nice algae bloom … and I didn't return the warm fluid to the stream, where it might have threatened the balance of the cold water ecosystem. Instead, I used the drainage to irrigate our alfalfa field.)

These two improvements worked very well, and I had the pond's surface temperatures in the 70's within a couple of days. It was a nuisance, though, to worry all the time about being home to stop the flow through the pipe at sundown or when a bank of clouds suddenly covered the sky. If any thermostatically operated water valves are available, I'd like to hear about them.






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