Q: I've been experimenting with cornmeal and other grains as food sources for the fish in my small farm pond, and I'd like to compress these various feeds into fish food pellets. Do you know where I can locate an inexpensive device that can press grain into small balls for use as homemade fish food?
The production of commercial pelleted fish feeds is a complicated process. Making a comparably complete, stable product at home is well-nigh impossible.
However, if your fish receive a fair amount of live or naturally occurring food (as is almost always the case in outdoor ponds at moderate population densities), you can make a useful supplemental feed. The available processing technology, however, may be either too small scale and tedious or too large scale and expensive for your needs.
To make very small amounts of feed, you can do as we did at the New Alchemy Institute for our feeding trials: Mix your ingredients with a hand grinder or a blender until you achieve a fairly stiff paste. Next, adapt a caulking gun to squirt this material out in a bead of the appropriate diameter (devices used in fancy pastry preparation should also work). Bake the resulting toothpaste-like material in an oven until it hardens, then chop or break it into pellets.
For production on a larger scale, you can use a commercial chopper to mix your ingredients into a sort of "spaghetti" of the diameter you desire. This feed, when frozen· and shaken in a bag, should break up into pellet-size pieces. The catch is the smallest commercial chopper you can buy (a 1/2-horsepower model) will set you back $1,000 or more.
You'll find that a mix which includes some meat or fish will hold together better than a vegetarian formula. However, if you'd rather not use fish or meat, there are food binders you can add to the meal. Old-fashioned commercial feeds contained sawdust, gypsum, or white cheese for this purpose, while modern preparations may include algin (a kelp extract) or gelatin.
The only way to find out how a given mix will pelletize is, unfortunately, by trial and error. Therefore, before making up large quantities of the feed, you should test your concoction for acceptance by the fish and for stability in the water. The pellets should retain their form long enough for the fish to find and consume them, which can take anywhere from 15 minutes to an hour, depending on the kind and number of fish.
And as far as storage goes, the only satisfactory method that I know of is freezing. Even so, it's best to make up small lots of feed frequently, or much of the nutritional value will be lost.
Bill McLarney, Ph.D., is a founder of the New Alchemy Institute and its sister organization in Costa Rica. He is the author of several books and numerous technical papers and articles on aquaculture.