The effects of nitrite on growth performance of clown knifefish (Chitala chitala) were evaluated in a 90-day experiment with fish body weight 10g-12g. The 96-hour median lethal concentration (96-hour LC⁵⁰ for nitrite) was 360 mg/L. The experiment was arranged randomly with nitrite (NO₂–N) concentrations of 180 mg/L (50% of LC⁵⁰-96h); 18 mg/L (5% of LC⁵⁰-96h); 10 mg/L (limited concentration for culture fish) and control. After a 90-day experiment survival rate, daily weight gain, specific growth rate decreased with increasing ambient nitrite concentration from 95±3%; 0.40±0.02g/day; 1.56±0.04 %/day at control to 59±6%; 0.25±0.02g/day; 1.18±0.07%/day at 180 mg/L treatment respectively whereas FCR grew up with increasing of ambient nitrite concentration from 3.88±0.12at control to 4.56±0.11 at 180 mg/L treatment. However, there was no significant difference among fish subjected to 0; 10 and 18 mg/L NO₂–N in specific growth rate with 1.56±0.04; 1.52±0.06 and 1.45±0.07%/day respectively. Similarly, the results of survival rate, daily weight gain and FCR from concentrations with 0 and 10 mg/L NO₂–N did not show any significant differences. At 10 mg/L treatment, survival rate, daily weight gain and FCR are 92±3 %; 0.38±0.03 g/day; 4.03±0.14 respectively. In some commercial cultured ponds of clown knifefish (fish body weight under 100g - 300g), the NO₂–N concentration of water samples was analyzed just to be around 0.5 mg/L.