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.
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.
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:  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.  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.
An aquaculture workbook by the New Alchemists — The Backyard Fish -Farm, published by Rodale Press — contained a discussion of a water filter consisting of broken clam shells. (That work has now been superseded by more recent studies. A bibliography of various other publications on aquaculture is available from New Alchemy Institute East — MOTHER.) The New Alchemists' guide gave me the idea of throwing eggshells into my unfiltered pond. This practice, I think, has two advantages: The fish eat the egg whites left sticking to the inside of the shells, and the remaining material provides a substrate for bacteria that purify the water. After a couple of weeks in the pool, the shells begin to grow black, powdery-looking colonies … and by the time the pond is drained for harvest, they've softened a bit and are half or more covered with the dark coating. Meanwhile, they gradually work their way across the bottom of the pool — along with fish excreta and all other wastes — to the center of my dish-shaped tank.
Adult tilapia, as I've already mentioned, can live on algae alone, and the tiny water plants are also a major portion of the young fishes' diet. It can be difficult to keep the algae level at the proper density … but I've been able to maintain a rich bloom, so thick I can't distinguish my fingers held in the water at arm's length. The color has nearly always been the bright green that indicates vigorous growth. A slightly brown cast — showing a degenerate condition — has occurred only twice.
Since our stream water is high in nitrates because of runoff from surrounding wheatfields, I've fertilized the pond just once (by placing a burlap bag containing nine pounds of duck manure in the center of the tank). About every three weeks I've drained part of the pool's contents from the bottom, and replaced it with fresh liquid. The waste has gone to a corn and buckwheat patch (my other gardens are irrigated from a duck pond).
My fish have never seemed very interested in the other greens I've tried on them. Alfalfa, cabbage, spinach, broccoli and chard were eaten only after they had rotted. Leaf lettuce and carrot tops were nibbled fresh, but in very small quantities. In fact, since their first month in the pond I've never seen the big tilapia eat anything.
The young fish, though, need a lot of protein, and I've experimented with various ways to provide it. During a period that I spent harvesting carp at nearby Lake Roosevelt, I grew maggots in quantity … a very messy operation and one I wouldn't mind doing without.
Raising mosquito larvae for the Tilapia has proved much easier and more pleasant and here's how my mosquito farm works: I collect a dozen five-gallon buckets which I fill from the pool and set outside the dome. (Much to my surprise, I've learned that mosquitoes prefer to lay their eggs in just plain pond water rather than in the manure-, grass-, or powdered milk-enriched solutions that I first tried.) Each morning I check for fresh egg rafts, and generally find two or three. If these have been laid in pails that already contain an adequate wiggler population, I move the floating masses of eggs to the freshest pail in the series. Whenever a batch is mature I dump the whole works (half the water has evaporated by then) into the pond and watch the fish scramble for the eggs. This system will produce about 100 wigglers every second day if I have enough buckets to start with.
Even so, I sometimes have to feed my fish oatmeal when I have nothing else ready for them. (I consider wheat bran a better food, but the tilapia don't agree.) My goal for the future is to use only rations produced on the farm … and that lets out both oats and wheat: I'll never grow either grain because of the huge amounts of time and labor necessary to process them by hand.
My first breeder to release her free-swimming young — 27 of 'em — did so July 14th. All of the season's later spawn were free swimming between July 21 and late August. They numbered 700 to 900 (about 60 to each batch) and weighed in at 58 live fish to the ounce.
The young tilapia spent their early days in their mothers' mouths, leaving only to forage and then returning for safety. Although the adult fish could never be seen unless I sat perfectly still on the observation plank for about 15 minutes, the young stayed close to the surface during the day and showed little fear of my presence. When a parent saw me, it was always she and not her babies that initiated a retreat. She'd simply inhale the spawn if they were closely grouped. If they were dispersed, she would dart at them a couple of times and cause them to bunch up. Later — when the young had grown so big that they would no longer all fit in their mother's mouth — this scene became quite comical. The little ones that got crowded out would struggle to jam themselves in, and, failing that, would try their parent's gill flaps or eyes … until the worried mama finally swam off and left them.
From the beginning of September on, the water temperatures in my tank began to slip below 70° Fahrenheit … down to 67° Fahrenheit on the 16th, the day of the first frost. Although I believe I would have had no trouble keeping the fish alive to the end of the month, there seemed little point in doing so since they don't grow at lower temperatures. I might have stacked manure around the north side of the dome to help keep it warm, but my truck was broken down at the time. Also, I had a full-time job then and couldn't have given the tilapia extra attention had they needed it.
The result was that I harvested my tilapia September 17, earlier than I hope to do this job in the future. I drained the pond nearly dry and dipped up the water in buckets, which I poured through screening to catch the fish. A check revealed that all my original stock had survived and grown to a length of six inches (a weight of one ounce each after removal of head, guts and scales). That was good news: The young fish I'd bought at a size of one and a quarter to one and a half inches had made it to six inches in just three months! The spawn harvested during the September draining (the fry born in July and August) measured one and three–quarters to two and a half inches and weighed an eighth of an ounce each. Had these babies lived and grown at a rate similar to that of the store-bought young, they would certainly have reached a length of six inches in five months. If I can improve conditions in the pool so that my tilapia spawn two or three months earlier in the year, then, I should end up with 1,000 fish dressing out to one ounce each. That's 62-1 /2 pounds of meat on the table … enough to keep me working on improvements to the system.
The six-inch tilapia were prepared like any small pan fish: beheaded, gutted and scaled, then rolled in cornmeal and fried. The taste was very close to that of. a similar-sized trout … a bit bland, but good.
I didn't want to waste even the tiniest fish, and spent considerable time separating about half of them from the debris in the bottom of the pond and pouring them through a couple of changes of water. I then threw them live into a boiling pot of chowder. The result was a disaster. The tiny tilapia partially exploded and something very bitter in their innards — possibly an organ like the gall bladder in mammals and birds — ruined the taste of the whole soup. In fact, I'm sure the looks alone would have spoiled it for most people! Next year I'll feed the small fry to the ducks.
My hope is to raise enough fish so that they and the ducks we keep will provide the protein we now get from machine harvested wheat, rice, and beans. When that happens we'll stop buying grains and grow more of our own easy-to-harvest potatoes to take their place. Then we can be truly self-sufficient in food.
One problem of living in a house heated only by a wood cook stove is that of maintaining the uniform temperatures needed by tropical fish in the winter. In fact, I didn't think it would be possible at all for me to hold breeders over until the next season. I did reason, however, that some of the smallest fish should be able to survive in unheated gallon jars in the houses of city friends. With this hope, I placed fish in the care of each of four different homes … figuring that one person at least would be sensitive enough to their needs. Two friends lost all their charges in a couple of weeks. A third had one survivor until December, and the fourth I have lost touch with. In addition, I kept fish of each age group in buckets in the house. All but one died during the first 36 hours … mainly, I suppose, of shock from all the handling they experienced. The single survivor, however, is still living happily in her five-gallon pail at this writing (February 1, 1974). Every right I put her on the cool side of the cook stove when the fire is going out for the night. The water temperature rises into the 90's, but usually falls to 56° Fahrenheit overnight and has been as low as 48° Fahrenheit. I leave the bucket on the stove in the morning until the water warms up to about 80° and then put it on the floor under a skylight for the rest of the day. The occupant is from the first spawn of the summer and has grown from about two inches to a length of three inches in her winter quarters. I hope Tillie makes it through until spring and becomes the brood stock for a super hardy strain of Tilapia mossambica.
One of my plans for the future is an addition to my house, containing an indoor, continuous-feed, horizontal, heated methane digester with a 2 foot x 2 foot by 8 foot ferroconcrete tilapia tank built right on top of it. The roof over this section of the building will be all fiberglass so that the fish will have plenty of sunlight as well as heat and space. Such a setup should make it possible for me to keep six- to ten-inch breeders over the winter, and maybe to do some preseason indoor breeding also (in a second 30-gallon tank I'm planning to build).
The other improvements I have in mind will be mainly in the production of fish food. To provide more high-protein supplements, 1 plan to start an earthworm bed. My heavily mulched gardens are full of worms, but I'd consider it robbery of the soil to feed any of them to the fish … and anyhow, harvesting the creatures from the ground would be too time–and labor–consuming. I'd even prefer to put my bed-raised worms into the earth rather than feed them to fish. Therefore, my primary tilapia feed-production effort will be aquatic.
My plan is to build three (at least) aboveground tanks one foot high, two feet wide and a minimum of eight feet long. Ferroconcrete is again desirable for permanence and easy maintenance, but I may use boards lined with plastic until the idea is proven. Alternatively, large discarded refrigerator bodies could be sealed with silicone rubber and used for containers.
I'll fill the tanks — one per week — with stream water, fertilize them lightly, and inoculate them with fishpond water and insect larvae from the creek. Each week (beginning 21 days later) I'll pick a warm, sunny morning to start draining one tank's volume of water from the bottom of my fishpool. In the afternoon, when the insect containers are hottest, the one with the three-week-old contents will be emptied into the domed pond while I scrub the vat's bottom and sides with a straw push broom.
I believe this system of rotating tank culture will provide the tilapia with the most natural free food supply I'll ever be able to manage … and, in the long run, do it with the least labor. The tanks also increase the effective surface area and volume of my pond without the expense of roofing. (If I like, I can glass over the two foot-wide containers simply by bridging them with old windows salvaged from house demolition. I wouldn't want to cover them completely, of course, since the insects then wouldn't be able to lay eggs in the vats.)
Fish — which require less land use and capital investment than warm-blooded animals — are, to my mind, the best hope for northern homesteaders to balance their protein needs on strictly home–grown feed. Thus I find my tilapia ecologically and economically satisfying. Maybe best of all, though, is the feeling I get when I walk into the rich tropical air of my fish dome and lie on the observation plank with my eyes looking up at the center and my arms floating in the pool of life. For an old Pisces like me, that's pure euphoria.
A gloomy footnote to my article "How to Raise Fish for Food at Home": This year we had young tilapia — some of them Tillie's offspring — by June 21 and hoped to get 700 to 800 up to the six inch size before harvest. Then, in mid-August, came a freak cloudburst that caused the worst flood we've ever seen in our ten years here. The deluge not only washed out part of our garden but also filled the fish dome with silt and cold water. In shoveling the slop out two days later I was surprised to find a lot of fish still alive … but the task of separating them from the mud was too difficult to stick with beyond getting enough breeders for next year. Also, most of the big ones (including Tillie, I'm sorry to say) died when I transferred them to the greenhouse early in October.
This year's experience did teach me some things (apart from the need to build a dike against one-in-ten-years floods!). First, a couple of points about the aquatic food raising program.
 In our water, at the temperatures we maintain, the cyclic buildup of algae will peak only three days after fertilization. The plants then begin to decay and are consumed by aerobic bacteria. This creates a poor environment for raising insects. The answer seems to be not to fertilize the water until the larvae get a good start.
 The quantities and species of insects that lay their eggs in the rearing tanks depends on the weather and the time of year … factors I can't control. I did learn, though, that containers with their surfaces close to ground level (like a natural pond) would attract more of whatever varieties were around.
I'm glad to say that the produce of my insect-raising tanks, with supplements of chopped earthworms and maggots, has enabled me to stick to my purpose of feeding home-grown rations only to my tilapia this season. One more note: I had a cannibalism problem with the fish this year and next season will isolate the breeders in a nylon net pen in the center of the pool.
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