Relative Growth of Lettuce (Lactuca sativa) and Common Carp (Cyprinus carpio) in Aquaponics with Different Types of Fish Food

Abstract

Aquaponics has the potential to contribute to food security in urban Nepal, where agricultural land near cities is rapidly being converted for other uses. This technology’s use is expanding in Nepal, but the relatively high cost of commercial fish food is a hindrance. As a result, some aquaponics operators are resorting to alternative, less expensive fish foods. Since the primary input of nutrients to the plants grown in aquaponics comes from the fish food, an evaluation of the impact of fish foods on plant and fish growth is needed to help operators evaluate the costs and benefits of commercial compared to alternative fish diets. This study evaluated the growth of lettuce and common carp, the most common species of plant and fish used in aquaponics in Nepal, with three fish diets (commercial fish food, commercial chicken food, and a homemade diet with mustard oil cake and rice bran) at a commercial aquaponics farm with nine identical systems allowing for three replicates of the three fish food treatments. There were no significant differences in the measurements of lettuce growth (stem length, root length, and stem mass) and few differences in nutrient concentrations in leaf tissue. The specific growth rate of the carp fingerlings was lowest for the fish in the systems fed with the homemade diet (0.21) compared to those fed commercial fish food or commercial chicken food (0.31 and 0.28, respectively). These findings suggest that aquaponics operators who have been buying the more expensive commercial fish food with fish meal as its protein source can save 50–95% of the related costs by using commercial chicken food or the homemade diet defined in this study. This could potentially encourage the expansion of aquaponics systems in Nepal.