The experiment was conducted to evaluate the effects of beta glucan, the plant extract, Vitabio A, and the plant extract with probiotic Lactobacillus spp. (Vitabio B) on the growth, histology and immune response of Labeo rohita (Rohu), reared for 120 days in a flow through system. Fish with an average body weight of 264±2.65g were stocked in cemented tanks at 10 fish/replicate. Four iso-nitrogenous artificial feeds containing 0.1% of beta glucan, plant extract, plant extract+probiotic and control (without any immunostimulants) were given to fish twice a day at 3% body weight of fish. A significant (p<0.05) difference in weight gain was observed between the control and plant extract fed group while it was non-significant (p>0.05) for the other treatments. The total serum proteins and cell counts (CBC) showed non-significant (p>0.05) difference among all the treatments except for RBC and Hb which were significantly higher in T1 (control) and T2 (plant extract + bacteria Lactobacillus spp.) compared to T3 (beta glucan) and T4 (plant extract). The analysis of fish body composition revealed that plant stimulant treatment had significantly higher crude protein and ash contents compared with the other treatment groups and lower fat content compared with the control (T1). In conclusion, the plant extracts and beta glucan can be used without any adverse effects on growth, total serum proteins, hematology and fish body composition.