Abstract:

To meet the demand for high-performance biofilter media in aquaponics systems, a closed-loop aquaponics system was established with 5 treatments: volcanic stone (T1), zeolite (T2), maifan stone (T3), ceramsite (T4), and mixed stones (T5). The impact of these media on water quality indicators, lettuce growth, and fish performance was analyzed, and the underlying mechanisms were explored in relation to the pore structure and chemical composition of the materials. The results indicated that the volcanic stone group (T1) significantly optimized water quality compared to other media. The concentration of ammonia nitrogen decreased to 0.70 mg / L, the concentration of nitrite was the lowest, and the average dissolved oxygen was as high as 7.64 mg / L. In T1, lettuce root length (375.06 cm) and root volume (13.47 cm³) increased significantly, the net photosynthetic rate reached 16.32 μmol/(m²·s), and the yield was 35674 kg/hm², all of which were higher than that of other treatments. Furthermore, the crucian carp in T1 achieved a weight gain of 147.67 g, and the serum aspartate aminotransferase (AST) level significantly decreased to 392.20 U/L. In contrast, while the zeolite group (T2) showed the lowest total phosphorus at the end of the experiment (4.52 mg/L), its ammonia nitrogen accumulated to 1.35 mg/L, leading to physiological stress in the fish with AST levels rising to 753.03 U/L. The maifan stone group (T3) significantly increased the soluble protein content of lettuce to 29.18 mg/g and maintained good health indicators in the fish. The mixed stone group (T5) did not demonstrate the expected synergistic advantages. In conclusion, volcanic stone performs best overall in improving water quality, promoting lettuce growth, and maintaining fish health, and its high porosity and specific surface area facilitate microbial attachment and nitrogen transformation, making it a highly efficient biological filter medium for aquaponics systems. These findings provide a valuable reference for the development of water-saving facility agriculture in arid and semi-arid regions.

Key words: aquaponics system, mineral filter stone, water purification, lettuce yield increase, fish health