This study investigated the effects of different concentrations of probiotic Pediococcus acidilactici on the total number, Specific growth rate, attached egg number and microbial count (lactic acid and total aerobic bacteria) in culture water and body of marine rotifer Brachionus plicatilis. The experiment was conducted as a completely randomized design in four groups: first group fed probiotic at 0. 5×106 CFU ml-1 (P1), the second group fed probiotic at 1×106 CFU ml-1 (P2), the third group fed probiotic at 1. 5×106 CFU ml-1 (P3), and the last group fed without probiotic (NP, control). Rotifers were cultured in standard conditions at an initial density of 30 ind. ml-1 using a 2. 5×106 cell mL-1 of Nanochloropsis oculta. Based on the results, the maximum number (215± 4. 91 ind. ml-1) of rotifers were significantly obtained after ten days in the third group in comparison to other treatments (P<0. 05). In addition, the highest growth rate (0. 46± 0. 023 ind. ml-1) and shortest doubling time (1. 5± 0. 14 days) were obtained in the treatment P3 but no significant difference was found between NP and other groups (P>0. 05). Moreover, it was revealed that the total aerobic bacteria was significantly related to the 3rd group that found be 1. 80×103 CFU rotifer-1 and 34. 0×104 CFU ml-1 in rotifer body and culture water, respectively (P<0. 05). Nonetheless, lactic acid bacteria of rotifer body and culture water was not concentration-dependent and the highest number of lactic acid bacteria in rotifer body (50. 58± 6. 08 CFU rotifer-1) and rotifer culture water (4. 43± 3. 28×103 CFU ml-1) was obtained in the treatments of P1 and P2, respectively. In conclusion, the present study showed that the bacteria P. acidilactici with N. oculta algae provide a higher growth rate and total aerobic bacteria in rotifer B. plicatilis.