Development of a bio-green floating system (BFAS) for the improvement of water quality, fish health, and aquaculture production.

Aquaculture activities often lead to environmental deterioration due to discharges of nutrient-rich wastewater without treatments. The present study aimed to develop a bio-green floating system (BFAS) to utilize excess nutrients, improve water quality, enhance plant and fish production, and minimize threats of aquaculture effluents. The floating raft system was constructed using water spinach integrated with a substrate (lava rock) to allow the development of biofilm communities, which together with the plants, improved the water quality by nutrient sequestration. Three treatments were employed for 105 days: (1) zero water exchange without BFAS (T1-NCT); (2) water exchange at 5-day intervals without BFAS (T2-PCT); (3) zero water exchange with BFAS (T3-BFAS). Total ammonia removal was significantly (p < 0.05) higher (92.4 ± 1.2%) in T3-BFAS compared to T2-PCT (89.2 ± 0.5%). The percent removal of other nutrients such as unionized ammonia, nitrite, and soluble reactive phosphorus was significantly (p < 0.05) higher in T3-BFAS compared to T2-PCT and the control. The T3-BFAS showed a significantly (p < 0.05) lower feed conversion ratio (FCR, 1.16 ± 0.05), higher (p < 0.05) specific growth rate (SGR, 3.58 ± 0.03), and better health indicators (hemato-biochemistry characteristics) compared to the other treatments. Heavy metals in T3-BFAS were significantly lower (p < 0.05) than the control and were significantly higher in roots than in the water. The findings suggested that the simple newly developed energy-free BFAS could enhance water quality, improve fish health, and optimize fish production in an aquaculture system without water exchange. [ABSTRACT FROM AUTHOR]