Formulated Diet Instead of Chilled Fish Is Beneficial to Microbial and Water Quality in Mandarin Fish (Siniperca chuatsi) Ponds.

The Mandarin fish (Siniperca chuatsi) is a valuable carnivorous species that is traditionally farmed alongside chilled fish. This practice often degrades water quality and threatens sustainability. In this study, pond environments under two feeding regimes, including chilled fish (CF) and formulated diet (FD), were compared through water quality assessment and high-throughput sequencing of both bacterial and microeukaryotic communities. The FD group exhibited significantly lower concentrations of ammonia nitrogen, nitrite, phosphate, and salinity, alongside distinct microbial assemblages. Bacterial communities in FD ponds were enriched with Proteobacteria and Bacteroidota, whereas CF ponds contained higher abundances of Actinobacteriota and Cyanobacteria. Microeukaryotic communities shifted toward Cryptomonas dominance in FD ponds, while CF supported more chlorophyte- and ciliate-associated taxa. Network analysis further revealed that FD promoted more integrated and resilient microeukaryotic interactions. Collectively, these findings demonstrate that formulated diets were conducive to keep water quality and restructure microbial communities, highlighting their potential as a sustainable feeding strategy to enhance ecological stability and reduce disease risk in aquaculture ponds.