Nine treatments, control group (D0), Lactobacillus acidophilus 1×10⁶ CFU g⁻¹+2g prebiotic mixtures kg^-1 (D1), L. acidophilus 1×10⁶ CFU g⁻¹+2.5g prebiotic mixtures kg^-1 (D2), L. acidophilus 1×10⁶ CFU g⁻¹+3g prebiotic mixtures kg^-1 (D3), L. acidophilus 2×10⁶ CFU g⁻¹+2g prebiotic mixtures kg^-1 (D4), L. acidophilus 2×10⁶ CFU g⁻¹+2.5g prebiotic mixtures kg^-1 (D5), L. acidophilus 2×10⁶ CFU g⁻¹+3g prebiotic mixtures kg^-1 (D6), L. acidophilus 3×10⁶ CFU g⁻¹+2g prebiotic mixtures kg^-1 (D7), L. acidophilus 3×10⁶ CFU g⁻¹+2.5g prebiotic mixtures kg^-1 diet (D8) and L. acidophilus 3×10⁶ CFU g⁻¹+3g prebiotic mixtures kg^-1 (D9) were added to the experimental diets of red tilapia fingerlings, Oreochromis sp. The average body weight of fish was 4.14±0.02g and distributed at a rate of 10 fish per 168 liters aquarium. Two aquaria have been assigned for each treatment. The highest final weight, weight gain, final length and growth rate were obtained for D6 group. Whereas the best feed conversion and feed efficiency were observed in D4 group. D8 was significantly higher in HSI, VSI, and RGI. The highest value of total protein was recorded in D2 group. Histologically, D1 shows a normal villous architecture. D7, D8, and D9 groups show high improvement with normal villous architecture and improvement of length, muscular layer thickness, and increased number of villi and goblet cells. As compared to the control-fed fish, the mixture of synbiotics is promising as an immune enhancer in aquaculture fish.