Effects of Crude Protein Levels in Diets Containing MKP on Water Quality and the Growth of Japanese Eels Anguilla japonica and Leafy Vegetables in a Hybrid BFT-Aquaponic System

This study investigated the effects of crude protein levels in diets containing monobasic potassium phosphate (MKP) on water quality and the growth of Japanese eels Anguilla japonica and leafy vegetables in a Hybrid BFT-Aquaponics (HBFT-AP) system. The first experiment (EXP1) was designed to verify the effects of the feed itself on leafy vegetable productivity using two diets (CP48 and CP30) with MKP and one commercial eel diet (COM58). The second experiment (EXP2) examined the effects of the three diets on productivity of the fish and leafy vegetables in the HBFT-AP for 6 weeks. After the 6 week feeding trial, the weight gain, feed efficiency, specific growth rate and protein efficiency ratio of fish fed COM58 and CP48 were higher than those of fish fed CP30 (P<0.05) and the growth of the four leafy vegetables was the highest with fish fed CP48. Water quality was measured six times per week using a portable water quality meter and reagent measurements and showed variance with time for TAN (0.01-0.09 mg/L), NO2-N (0.010-0.064 mg/L), NO3-N (5.52-27.15 mg/L), PO4-P (2.03-5.32 mg/L) and pH (7.86-6.15).