The effect of stocking density and the application of Nitrobacter as ammonia decomposer in aquaponics system of Clarias gariepinus with water spinach (Ipomoea aquatica)

This study aimed to determine the effect of <em>Nitrobacter</em> bacteria on specific growth rate (SGR), survival rate (SR), and feed convertion ratio (FCR) of African catfish (<em>Clarias </em><em>gariepinus</em>) in aquaponics systems. The sample used was African catfish with a size of 5-7 cm as many as 720 individuals. The research method used was experimental design in the form of Completely Randomized Design (CRD). This study used 5 types of treatments with 4 repetitions. The P0 and P1 contain of 30 fish in each aquarium; 35 fish in P2; 40 fish in P3; and 45 fish in P4. The control group (P0) were treated without <em>Nitrobacter</em> administration and the other 4 intervention groups were given <em>Nitrobacter</em> 1 ml with a density of 1x10⁸ CFU ml^-1. The main parameters studied were SGR, SR and FCR of African catfish in different aquarium with different stocking densities. This research also studied the growth of water spinach (<em>Ipomoea aquatica</em>) also water quality conditions in aquaponics systems. The administration of <em>Nitrobacter</em> in aquaponics systems gave a significant effect on the SGR, SR, and FCR of catfish. The administration of <em>Nitrobacter</em> in an aquaponics system can give maximum effect if there are 45 fish stocking densities and 1 ml <em>Nitrobacter</em> with a concentration of 1x10⁸ CFU ml^-1.