The performance, efficiency of consumed feed, body chemical composition, survival rate, antioxidant and immunity parameters of Nile tilapia (Oreochromis niloticus) reared in probiotic-treated water were studied. Two hundred apparently healthy Nile tilapia (20 ± 0.3 g) juveniles were reared for 70 days in five different treatments, with five replications as the control group (clean water) and four test groups with two probiotics strains (Bacillus toyonensis and Geobacillus stearothermophilus) at two different levels (1 or 2 × 105 CFU ml− 1) applied in rearing water. Fish reared in water supplemented with G. stearothermophilus at low level demonstrated significantly enhanced (p < 0.05) growth performances in terms of final body weight (FBW), weight gain (WG), daily weight gain (DWG), specific growth rate (SGR), and relative growth rate (RGR) compared to the control group. In the same context, supplied fish rearing water a lower amount of G. stearothermophilus (GS1) remarkedly reduced feed conversion ratio values when compared to the control group. In contrary, all other feed efficiency parameters increased significantly when G. stearothermophilus (GS1) water was added at low amount in the compartment with the untreated group. Moreover, probiotic water additives significantly reduced the range and median levels of unionized ammonia ( NH3) in water when compared to the untreated group. According to the findings of the body chemical composition, treated tilapia water with a high level of B. toyonensis had significantly higher crude protein and fat levels, as well as lower ash levels, than the control group. When compared to the control group, probiotic-water supplementation significantly improved oxidative status and immunological activity at all bacterial dosage levels, with the fish group enriched with a high level of G. stearothermophilus recording the maximum values of both antioxidant and immune activity. Finally, results reveal that water treated with B. toyonensis or G. stearothermophilus as a probiotic promoted Nile tilapia growth and health status, and this technology may be applied to stimulate tilapia productivity in culture farms.