The aims of this research were to study the impacts of mixed selective Bacillus sp bacteria on the growth of rotifers Brachionus plicatilis. The first experiment was investigated the effects of a mixture of  Bacillus sp and probiotic products on rotifer populations with two treatments and one control: (1) add without bacteria for the control samples, (​​2) add a mixture of Bacillus B7 + B41 (Bacillus amyloliquefaciens), (​​3) add Pro W probiotic products to culture rotifer tubes. In the second experiment, after accomplishing the first experiment, the whole experimental rotifers were infected with the cold bacteria of Virio harveyi to determine the survival rate of rotifers after the infection. Results showed that the density of rotifers, carrying eggs in the treatments added with Bacillus bacteria, was significantly higher than those in the controlled conditions. In addition, the highest value was obtained from the treatments with an additional mixture of Bacillus B7 + B41 (Bacillus amyloliquefaciens) that Bacillus bacteria possibly overwhelmed Vibrio bacteria. The rotifer productivity has been improved when adding Bacillus as well as microbial products into the feeding system. Rotifers in the experiment adding Bacillus can maintain a higher survival rate under the infection of Vibrio harveyi bacteria, but the difference was not statistically significant (P>0.05).