Seasonal and diel variations of nutrients viz. nitrate, nitrite, ammonia, soluble reactive phosphorus and silica in Banjara lake (identified by Andhra Pradesh Fisheries Department for pisciculture) during August 1986 to July 1987 were reported. Nitrate, nitrite and ammonia reached highest concentrations in March (3·76±1·74 mg l−1), July (575±77 μg l−1) and April (404·6±127 μg l−1) respectively. However, fish kills through nitrite toxicity was not observed at the reported nitrite concentrations. Ammonia decreased during summer mainly due to utilization by phytoplankton blooms. The highest value of soluble reactive phosphorus was observed in April (956±44 μg l−) attributed to sewage, domestic effluents and also release from sediments. Silica was at a maximum in October and decreased during diatom blooms in December. Clear pattern of diel variation was not observed for nitrate, nitrite and phosphorus. However, ammonia showed diel variation having higher concentrations at 6 h than 12, 18 and 24h due to its slower uptake by phytoplankton during nights. Chlorophylla was at a maximum in May (32 mg m−3) at N/P ratio of 5·3 with the dominance of cyanophyceae and chlorophyceae.