Due to growing interest in bacterial probiotic incorporation within juvenile marine finfish production, multiple commercial products are currently available. The following trial was conducted to test the effect of incorporation of a commercially available Bacillus spp. probiotic blend (EcoAqua) on population growth dynamics of the rotifer Brachionus plicatilis. Incorporation consisted of 0.1 mL L−1 daily probiotic additions directly to rotifer cultures and 0.1 μL mL−1 additions to feed mixtures during preparation. Probiotic-treated cultures’ daily mean populations were found to be significantly greater (Pα(2),4,4 < 0.05) on multiple culture days. This trend was confirmed as significant (Pα(2),1,45 < 0.001) using ancova. Logistic population growth curves fit for each treatment were statistically non-coincident (Pα(2),5,40 < 0.001). Substantial differences between treatment and control parameter estimates were observed; however, statistical comparisons could not be employed. Population variability was also reduced by probiotic inclusion as evidenced by lack of significant, positive correlation for probiotic daily population standard deviations (r = 0.0022, P = 0.99) and detection of a significant, positive correlation for control absolute value regression residuals (r = 0.50, P = 0.013) with Day of Culture. The tested bacterial probiotic improved rotifer culture population dynamics, suggesting potential production benefits from its utilization.