Freshwater ecosystems in India are experiencing significant eutrophication and a decline in biodiversity, which directly affects the goals related to clean water and sanitation, as well as the preservation of terrestrial life. This study assessed the efficacy of various water quality management interventions specifically, the restoration of riparian buffers, reduction of nutrients, and control of sedimentation on the recovery of fish communities at Pili Dam, Bijnor, Uttar Pradesh, over a period of two years (June 2022 to May 2024). A total of 1,845 individual fish, representing 27 distinct species from 11 different families, were captured, identified, and recorded through the study period. The results exhibited a notable improvements in dissolved oxygen rose by 85.7% (from 4.2 to 7.8 mg/L), total phosphorus diminished by 70.8% (from 120 to 35 µg/L), and turbidity decreased by 75.8% (from 18.6 to 4.5 NTU). The richness of fish species experienced a remarkable growth, rising from 12 to 23 species, while the Shannon diversity index saw a significant elevation from 1.45 to 2.89 (p < 0.001), thereby making a substantial contribution to Sustainable Development Goal 14 pertains to life below water. NMDS ordination demonstrated clear community clustering (R = 0.74, p = 0.002), accompanied by strong correlations between water quality and fish (r = 0.85–0.93). Our findings indicate that focused management of water quality effectively revitalizes fish diversity in dam ecosystems within a timeframe, thereby contributing to the advancement of Sustainable Development Goals 6, 14, and 15, and offering practical recommendations for the National Mission for Clean Ganga.