year per 100. To extend the growing 

 season for warm-water species, a 

 plastic dome can be built for $40. 



How does the system work? The fin- 

 gerlings are placed in the pool and fed 

 a commercial feed. The biological filter 

 and clarifier are used to remove the 

 large amounts of wastes fish produce 

 under the intensive feeding schedule. 

 The clarifier removes the solid wastes, 

 while the biological filter changes the 

 ammonia in the water, which is toxic 

 to fish, to nitrite then nitrate. The 

 nitrate is food for the algae in the pool. 



Van Gorder suggests stocking a 

 backyard pool with tilapia. Tilapia are 

 hardy fish, tolerant of a wide range of 

 water conditions. They grow quickly 

 in warm water. And, they taste good. 

 "They're almost boneless," says Van 

 Gorder. "They have a mild flavor, not 

 fishy. The meat is very white, not 

 mushy. To me it tastes better than 

 trout." 



Water quality can make a big dif- 

 ference in the fish you produce. "You 

 should test the water that you have to 

 make sure there's nothing in it toxic to 

 fish, or to people who eat fish," says 

 Van Gorder. The North Carolina 

 Department of Agriculture's 

 Agronomic Division will test water for 

 its nutrient levels. Send a small plastic 

 container half filled with water to the 

 Agronomic Division, Plant Analysis 

 Center, Blue Ridge Road, Raleigh, 

 N.C. 27611. 



Temperature is one very important 

 aspect of water quality. Tilapia, for in- 

 stance, grow faster when water tem- 

 peratures are above 70°F. All species 

 have an optimum water temperature 

 at which they grow best and have the 

 greatest resistance to disease or 

 parasitism. "There is a range of 

 tolerance above and below this tem- 

 perature within which the fish will sur- 

 vive, but with increasingly reduced 

 growth the farther the temperature is 

 from the optimum," writes Van Gor- 

 der. "For a fish-culture situation to be 

 economically feasible, the feed conver- 

 sion and growing season must be max- 

 imized to reduce feed costs and obtain 

 a harvestable-sized crop as quickly as 

 possible." 



One way to lengthen the growing 

 season in the fall and raise water tem- 

 peratures earlier in the spring is to in- 

 sulate the pool with plastic. Using an 

 inexpensive 3 /4-inch PVC frame draped 

 with six millimeter plastic to cover the 



pool, the backyard aquaculturist can 

 collect solar energy and store it more 

 easily. Plastic-draped pools also keep 

 water temperatures more constant. 



Another method for extending the 

 growing season is to raise fish in a 

 greenhouse. Under this efficient 

 method, the fish pool acts as a heat 

 sink, keeping waters warm for the fish 

 and storing solar energy for slow 

 release into the greenhouse at night or 

 on cloudy days. The nutrient-rich 

 pond water can also be used to fertilize 



plants growing in the greenhouse. 



To test other aspects of water 

 quality, many aquaculturists use a 

 water-quality test kit. Test for levels 

 of dissolved oxygen, nitrate, ammonia 

 and pH. The tests should be made 

 daily. Running the test and feeding the 

 fish take about 20 minutes daily, Van 

 Gorder says. 



Backyard aquaculture, like garden- 

 ing, is a means of self-reliant food 

 production, Van Gorder says. "We 

 (Rodale Research Center) don't ad- 



