Comparison of efficiency and nitrification process in an aquaponic system using two types of hydroponic subsystems

The efficiency and nitrification process in a lab-scale aquaponic system using two different hydroponic subsystems including the deep water culture (DWC) and nutrient film technique (NFT) were evaluated for 8 weeks. Common carp juveniles (Cyprinus carpio- average initial weight of 9.34 ± 0.06g at a density of 300 juveniles per m3 in fish culture tanks) and mint (Mentha spicata- 6 plants in each hydroponic subsystem) were cultured in triplicates in a green house facility. Water quality parameters such as pH, nitrate and ammonia levels were measured and compared at the end of every week. In the fourth week of the experiment, the pH of the DWC system was significantly higher than in the NFT (p < 0.01). Ammonia levels did not show any significant difference between the two types of aquaponic systems during the experiment (P> 0.05). In both systems, nitrate values showed an increasing trend from the third week to the end of the fourth week, followed by limited fluctuation until the end of the experiment. The nitrate levels in the NFT system were higher in the fourth, fifth, sixth and eighth week . The average total weight of the mint plant in the DWC was higher than that in the NFT system. Based on the results, the use of the DWC is recommended due to the better efficiency of the experimental culture system and better growth performance of fish and mint plant.