The value of food conversion ratio (FCR) showed no significant difference among treatments (p > 0.05). FCR is the amount of feed (kg) which is given to produce 1 kg of fish meat, and the best FCR in this study belonged to T3, followed by T2 and T1 (Table 2). The lower value of FCR indicates less food needed to produce 1 kg of fish meat. FCR of T3 (1.60) means that for the production of 1 kg tilapia, it is required 1.60 kg of food. The higher ammonia concentration of T1 caused inefficient FCR, when compared with T2 and T3. Ammonia caused high FCR, as a result of some of the energy used to process ammonia excretion. According to Hargreaves and Kucuk (2001), high FCR in line with the increasing ammonia concentration is due to digestibility of dietary protein, and energy sources may have been affected. FCR for nile tilapia generally ranges from 1.4: 1 to 1.8: 1 (DeLong et al. 2009). The average of FCR value was comparable with the 1.69 (tilapia in the aquaponic system with prawn) and 1.72 (tilapia in the aquaponic system without prawn) reported by Sace and Fitzsimmons (2013), and better than 1.81 and 1.86 (tilapia and hydroponics bell pepper), and 2.2 (tilapia without plant) obtained by Kamal (2006).