Alkalinity of water plays a vital role in body metabolism and physiology of fish and might have large influence on the growth particularly in early life stages. Several incidences of poor survival and mass mortality are coming up in hatcheries and nursery phase of Indian major carps. The present experiment was intended to study the influence of varied levels of alkalinity on the growth performance during a 30-days fry rearing of rohu. Different alkalinity range, viz. 60 (pond water), 100, 150, 200 and 250 mg as CaCO3/l were used as the five treatments T-1 (control), T-2, T-3, T-4 and T-5, respectively. The desired alkalinity for the treatments, maintained in triplicates, could be established by mixing the filtered pond water 60 mg as CaCO3/l alkalinity and ground water with 300 mg as CaCO3/l alkalinity at different proportion. The alkalinity levels were checked and maintained in every 5 day intervals with use of water in required proportion. Other important water quality parameters such as pH, total hardness, dissolved oxygen (DO), total ammonia (TAN), nitrite, nitrate and phosphate were estimated. Significant increase (P<0.05) in hardness was recorded with increasing alkalinity levels in the tanks. Both water pH and DO were lower in T-1, but increased significantly with increased alkalinity from T-2 and T-5 (P<0.05). Though there was statistically no difference in fry survival among treatments, it reduced with increased alkalinity. Similarly, no significant difference in the final total length was observed among the treatments. But, the harvested fry body weights in T-2 and T-3 were significantly higher than that of control as well as T-4 and T-5. Such result while indicted the alkalinity range of 100-150 mg/l to favour fry growth, exposure to more than 150 mg/l alkalinity reduced the growth, supporting the fact of stress being exerted on fry by the higher alkaline condition.