Dynamic root floating technique: An option to reduce electric power consumption in aquaponic systems

Aquaponics is an integrated system in which the water containing fish waste is used as a nutrient source for plant production in a closed recirculation system. In this study, tilapia (Oreochromis niloticus) and pak choi (Brassica chinensis) culture was tested using two techniques: 1) Root floating (RAFT), and 2) Dynamic root floating (DRFT). Water quality parameters, total ammonia nitrogen, nitrate nitrogen, nitrite nitrogen and phosphate were measured. At the end of the experiment, fish and plants were weighed and the required electric power consumption was calculated. There was no significant difference observed between the effect of each treatment group on either tilapia or pak choi production. Tilapia productivity was 1.69 ± 0.22 kg/m3 and 1.71 ± 0.23 kg/m3 and pak choi yield was 7.43 ± 1.23kg/m2 and 7.32 ± 0.76 kg/m2 for the RAFT and DRFT, respectively. Water quality parameters were within the recommended range for the tilapia culture while pH and conductivity were out of range for the pak choi culture; nevertheless, plant production was good. Total ammonia nitrogen and nitrite nitrogen did not reach concentrations that could impede tilapia growth. The DRFT allows the elimination of active aeration in hydroponic systems for tilapia and pak choi production during most of the cycle, reducing the electric power consumption to 10.3% and electricity costs to 11.4% by using a nature-based solution.