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Utilization of phytoremediated aquaculture wastewater for production of koi carp (Cyprinus carpio var. koi) and gotukola (Centella asiatica) in an aquaponics

Nuwansi, K.K.T., Verma, A.K., Rathore, G., Prakash, Chandra, Chandrakant, M.H., Prabhath, G.P.W.A.
Aquaculture 2019
Centella asiatica, Cyprinus carpio, ammonium nitrogen, animal growth, aquaponics, biofilters, color, feed conversion, fish health, growth performance, hydroponics, koi, leaf width, leaves, medicinal plants, nitrate nitrogen, nitrite nitrogen, ornamental fish, plant growth, protein efficiency ratio, specific growth rate, supply balance, vegetables, wastewater, water quality, weight gain
An experiment was carried out for 60 days to utilize the phytoremediated aquaculture wastewater for production of Gotukola (Centellaasiatica (L.)), a leafy vegetable as well as a traditional medicinal plant; and koi carp (Cyprinuscarpiovar. koi), a popular ornamental fish with high market demand. Treated water and borewell water were mixed in different combinations namely 100:0 (T1), 75:25 (T2), 50:50 (T3) and 25:75 (T4) to produce four treatments. Additionally three controls were also maintained to compare the efficiency of the treatments. These were Control 1 consisting of hydroponic component with plant (C1), Control 2 consisting of hydroponic component without plant (C2) and Control 3 with only borewell water (C3). Plants in Control 3 were used to compare the efficiency of plant growth in field condition. On the basis of plant growth parameters viz., leaf width, number of leaves, number of plant-lets, number of runners, length of runners and the final yield, T1 showed the best performances. However, it was not significantly different from T2 and T3 except the final yield. Best growth performance of fish viz., weight gain, length gain, feed conversion ratio (FCR), feed efficiency ratio (FER), protein efficiency ratio (PER), and specific growth rate (SGR) was observed in T3. Considering the fish colour, there was no significant difference between the treatments for chroma and hue values, but best chroma values were obtained in T1 followed by T2 > T3. This denotes that the treated wastewater positively affects the fish colour by pigment enhancement. The efficiency of the aquaponics was judged by percentage nutrient removal and biofilter performance. The highest removal of nitrite-N (92.34%), nitrate-N(70.55%) and ammonia-N (71.36%) were observed in T1 and it was positively related with the plant growth. The highest phosphate-P removal percentage (59.78%) and best biofilter performance (3.24 g−3 day−1) were observed in T3 and also, comparatively a higher plant growth was obtained in T3 than T4 and C1. Considering the overall parameters viz., fish growth, fish health, plant growth and water quality parameters, equal proportion of treated wastewater and borewell water (T3) was found to be the most effective combination. The results revealed that the phytoremediated aquaculture wastewater can be sustainably reused in aquaponics for fish and plant production.