Report On An Experimental Solar-heated Aquaculture System

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Then what I like to call the "free lunch rule" began to assert itself. (It's a basic truth of ecology that "there is no such thing as a free lunch" . . . and indeed, in working with my little ecosystem, I have had that law enforced on me many times. The fact is inescapable: You can't get something for nothing.)

What happened was that the fish were constantly hungry. The more I fed them, the more they ate, until my supply of earthworms couldn't keep up with the demand. Then I reread the Mahan article and learned that the authors are commercial earthworm raisers . . . an extremely significant fact that I hadn't previously considered.

Obviously, my four little compost bins were totally inadequate for producing the number of worms I needed. If one figures a minimum diet of one worm per fish per day, one finds he is using—assuming 55 fish—385 per week, 1,540 per month and 9,240 every six months. At a cost (in my area) of $20.00 per 7,000 earthworms, those fish dinners began to be anything but a "free lunch". The long-term solution, of course, is to create a much larger worm farm . . . one in which the creatures' natural reproduction is able to keep up with the need for fish food.

Meanwhile, in an effort to ease the demand on my hard-pressed earthworms, I attached a 12-volt automobile taillight bulb to the wind-electric system, hung it over the fish tank each night last summer, left the door and all vent flaps open and used the light to attract insects for the fish to 'eat. This system worked very well. Although I was apprehensive about bringing such visitors into the greenhouse, I needn't have worried. The bluegills must have gotten virtually every one of them, because I had no problems with insect damage to the plants. It became something of a pastime to "watch the fish eat". Each evening one could see them grouped in a huge circle around the light, waiting for any bug foolish enough to come within striking distance. Each morning a thin film of "leftovers"—insect wings, legs, etc.—covered the water.

That solution worked just fine for the summer months, but when the nights began to cool off and the bug population dwindled, it was back to an earthworm diet for the fishes. At this writing (October 1974) the worm supply which had accumulated during the summer is about exhausted, and the bluegills must soon be harvested . . . without, I'm sorry to say, having gained the size or weight I had hoped for.

An additional unforeseen problem is that the tank filtration system which appeared in the drawing of the ecosystem in MOTHER NO. 28 has proven to be impractical. This, you'll remember, consisted of three 55-gallon drums placed outside the greenhouse and filled with calcium carbonate (crushed oyster shells). The water from the fish tank was to be run through this filter in order to remove the growth-inhibiting metabolites produced by the fish. The necessity for such a precaution is explained by Dr. McLarney in Newsletter No. 2 of The New Alchemy Institute:

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