Abstract: In order to further explore the effect of floating bed coverage of Ipomoea aquatica on the water quality of Oreochromis niloticus aquaculture system, the experimental groups with 20% (C₂ group), 30% (C₃ group), 40% (C₄ group) of floating bed coverage of I. aquatica and the control group without floating bed coverage (C₀ group) were set up, and O. niloticus was fed by the satiation feeding method. Since the beginning of the experiment, water samples were collected every 7 days to detect the water quality. The specific detection indexes included the concentration of dissolved oxygen (DO), total ammonia nitrogen (TAN), nitrite nitrogen (NO₂^--N) and nitrate nitrogen (NO₃^--N) in the aquaculture water. At the end of the 35 d experiment, the growth indexes such as body length and body weight of O. niloticus were detected. The results showed that the water quality indexes and growth indexes of C₂ group, C₃ group and C₄ group were better than those of C₀ group. The TAN concentration of C₄ group was significantly lower than that in other treatment groups (P<0.05), and the NO₂^--N and NO₃^--N concentrations were also the lowest. Additionally, all growth indicators of O. niloticus in the C₄ group were superior to those in the other treatment groups. There were no significant differences in DO concentrations among the treatment groups (P>0.05). On the whole, the water purification effect of O. niloticus aquaculture system covered with I. aquaticawas better than that of traditional aquaculture. When the floating bed coverage was 40%, the water purification effect and fish growth indexes of the fish-vegetable symbiotic system were the best.

Key words: Oreochromis niloticus, Ipomoea aquatica, floating bed coverage ratio, water quality, feeding to satiation, growth status