Combined Effects of Eco-Substrate and Carbon Addition on Water Quality, Fish Performance and Nutrient Budgets in the Pond Polyculture System

Abstract

Traditional aquaculture can cause serious environmental pollution. Biofilm and biofloc technology have the potential to limit aquaculture pollution. An outdoor experiment was conducted to evaluate the combined effects of eco-substrates and carbon addition on water quality, fish performance and nutrient budgets in the pond polyculture system. In the treatment group, the total ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, and total nitrogen of the water were significantly lower compared to the control group (p < 0.05). The growth performance of H. molitrix and A. nobilis, including the final individual weight, specific growth rate, weight gain rate, total production and net production, was significantly higher in the treatment groups compared to the control (p < 0.05), while there was no significant difference in those of C. carpio between the two groups. Feed was the main N (>92%) and P (>95%) input during the experiment. Comprehensive accumulation was the main N (>58%) and P (>69%) output. The N and P feed input and comprehensive accumulation output declined in the treatment group. The N utilization efficiency in the experimental group increased slightly (p > 0.05), while the P utilization efficiency in the experimental group was significantly higher compared to the control (p < 0.05). Therefore, the application of eco-substrates and carbon addition can increase water quality, improve fish growth, and promote nutrient utilization efficiency in pond polyculture systems.