Fish Farm with Cages!

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NATURAL FEEDS

All of the fishes mentioned here, with the exception of the sunfish, can be reared on a 100% processed food diet. (Although most sunfish will eat some commercial feed, they really don't make good use of it.) Of course, all fish will eat available natural foods. I'll describe five of the ways you can provide your caged livestock with "fresh victuals" ... the possibilities are legion.

Bug lights: The Will-O'-the-Wisp Bug Light Fish Feeder—available for $154.19 postpaid from Hedlund of Medford, Dept. TMEN, P.O. Box 305, Medford, Wisconsin 54451—consists of an ultraviolet light and an impeller fan. Nightflying insects attracted by the light are sucked in by the fan and blown into the water. The unit can be mounted directly over a cage and costs pennies a day to operate. And although trout and bluegills particularly relish floating bugs, almost any species of fish will learn to eat them.

The Trail Lake Feeder: The Trail Lake Feeder is a do-it-yourself, low-tech way to provide caged fish with a good supply of insects ... in this case, fly maggots. To construct the unit, mount a hardware cloth basket on a pole a few feet above the cage. Wrap some form of rotting meat or fish—road kills are OK—in moistened paper, set it in the basket, and then let nature take its course. As the many maggots that appear mature and seek to pupate, they'll move away from their food and fall into the water. (You'll need to replace the decaying meat weekly.)

Earthworms: If you raise earthworms, you can construct a special feeder by simply punching a few holes through a thin block of polystyrene foam. Spread some worms on that and float it in the cage. As the crawlers burrow their way down through each hole, the fish will eat them.

Scrap and offal: If you have a source of unwanted fish, meat scraps, or offal, you can use these leavings by grinding, chopping, or boiling them. Any food particles that are so small they might pass through the mesh should be placed in a large container and lowered into the cage.

Green plants: Although most of the fishes I've discussed will not eat leafy matter, tilapia are quite fond of plants and Israeli carp will take some. Most soft aquatic plants, comfrey, purslane, carrot tops, and hairy vetch can be used. Serve the vegetation by tying it in bunches and hanging it in the cage.

Although you may not be able to provide much natural feed, keep in mind that even an amount totaling less than 1% of your fish's total diet may improve their growth or flavor ... or even enable you to switch from a complete commercial feed to a less costly supplemental one. (Remember to allow for water content when calculating feeding rates—or ratios—with natural feeds. Commercial products are relatively dry, while insects contain approximately 75% water ... fish, meat, and worms about 85% ... and green plants 90 to 95%.)

MAINTENANCE Inspect your cages daily. When necessary, clean the mesh so any accumulated algal growth won't inhibit water flow. (A toilet brush mounted on a long handle works fine for this purpose.) You should also examine the fish to see that their feed is being eaten and that they're in good health. If food is being wasted, cut back on the amount ... skip a day's serving ... or change their diet.

If your stock remains off its feed after you've taken the above measures, check the fish for disease. It isn't feasible to discuss all of the potential health problems here. (Consult The Freshwater Aquaculture Book, or a diagnostic service listed in the 1983 Buyer's Guide, if you suspect a malady.) Disease can do damage but—to put the matter in perspective—let me mention that in six years of raising bullheads and sunfish at New Alchemy (excluding the mysterious brown bullhead deaths I talked about) we had one disease outbreak, and that resulted in only about 10% mortality.

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