A 126-day feeding trial was conducting on ornamental fish, Oscar (initial weight: 13.12 ± 1.34 g) to examine the effect of probiotic bacteria, Pediococcus acidilactici on the growth performance and innate immune response. The experimental diets were the consumed feed as control (C), C with fish-oil (O) or the probiotic and fish-oil (PA) and fed ad lib twice a day (n=3). The growth indices including specific growth rate (SGR), feed conversion ratio (FCR)) and immunological indices of fish fed the diets such as lysozyme activity, total immunoglobulin and alternative complement activity were measured. Fish fed the diet containing P.acidilactici (PA) displayed significantly (P<0.05) higher final weight (32.22 g), weight gain (54.14 %), SGR (2.15 %/day) and lower FCR (1.05) compared to those of other experimental diets. Total immunoglobulin (9.8 μg/ml), lysozyme activity (3.5 μg/ml) and alternative complement activity (2.1 U/ml) in the serum fish fed the diet PA were significantly (P<0.05) higher than those of fish fed the diets C (8.9 μg/ml, 3.0 μg/ml and 1.0 U/ml) and O (7.9 μg/ml, 2.4 μg/ml and 0.7 U/ml), respectively. The results showed the positive effects of Pediococcus acidilactici as a potent probiotic on growth performance and non-specific immune system of Oscar.

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