The study was conducted to assess the application of Chlorella sp. and baker’s yeast Saccharomyces cerevisiae in feed rations and the frequency of water change in improving the population growth of the freshwater rotifer Brachionus calyciflorus. Rotifers were inoculated at 200 rotifers/mL in 10 L jars containing 8 L of disinfected freshwater. The results show that while the highest density of rotifers (655 rotifers/mL) was obtained in the combination of 75% algae + 25% of bread yeast, it was not significantly higher (p > 0.05) than the culture where rotifers were offered solely algae. The growth of the rotifer population was also improved by the frequency of water change per day, and the density reached 855 rotifers/mL, which was not significantly higher than that of water change every 2 days, but significantly higher than the culture where water change was not applied. These results confirmed that rotifers B. calyciflorus reached the highest density when fed 75% algae + 25% yeast with water change applied daily.