Traditional brackish water aquaculture farms in North 24 Parganas district of West Bengal, India receive sewage water from Kolkata metropolitan city through Bidyadhari River and its tributaries diluted by mixing with sea water. These areas play important ecological role by improving water quality, through conversion of nutrient load into fish biomass. Efforts are underway by farmers to increase production by increasing stocking density of fishes along with fertilizer and feed application. Effects of production levels of enhanced low (1.62±0.12, EL), medium (2.34±0.09, EM) and high (2.93±0.21, EH) over existing production level of 0.87±0.06 (EC) tons/ha/year on the effluent quality compared to source water (SW) was studied for 10 months production cycle. Dissolved oxygen concentration and pH was similar in effluents from EC, EL and EM while those were significantly (p< 0.05) low in SW and EH. Chemical oxygen demand (COD) of effluents from EC and EL were similar and ranged between 10.97-12.02 ppm whereas significantly (p< 0.05) higher in EH (17.07±3.27) and SW (19.55±4.83) while it was moderately high in EM (13.96±2.55). Similar trend has been observed in case of NO3-N, NO2-N, NH4-N and PO4-P. A drastic depletion of bacterial population was observed in all treatments compared to SW. Production from this system can be increased up to 2.34 tons/ ha/ year keeping intact the ecological role.