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The purpose of this study was to investigate the appropriate density of the recirculation aquaponic system of nile tilapia culture. An aquaponic system was studied through the integrated culture of nile tilapia and red Oak lettuce in a recirculating system for 120 days. Tilapia fry of uniform size of 7.13, 8.00,
7.67 g, and the average length 8.27, 7.29, 6.68 cm were released in 0.5 m 3 cement tank in three treatments (stocking densities) with 3 replications: 150, 250 and 300 fish/m3 to access the effect of stocking density on the growth performance of fish. Fish were fed with commercial feed, Ad libitum. The results showed that
weight gain of nile tilapia were 27.82, 43.32 and 39.90 g and the average length gain were 14.58, 18.25 and 13.10 cm, respectively. The survival rates were 92.44, 97.00 and 97.33%, respectively. However, there were no significant differences between the treatments. The average daily gain were 27.89, 23.17 and 27.93
g/day, The feed conversion ratios were 0.07, 0.19 and 0.09, respectively. The Specific growth rate were 23.18, 36.10 and 36.10 percent/day, respectively, and was significantly different among the treatments. There were no significantly differences in the temperature, DO, nitrate and phosphorus among treatments.
However, the value of pH was significantly different ranging between 7.36-7.51. Therefore, recirculation aquaponic system can be considered a sustainable aquacultural production.