Rotifers Brachionus plicatilis are the most common zooplankton used to rear eairly larvae of marine shrimp and finfish. Reduce production cost of live food in marine hatcheries is considered one of the main targets for developing a marine aquaculture industry. The present study is conducted to investigate the population (as increase in number) and population
growth rate of rotifer Brachionus plicatilis fed on un-live microalgal diet, frozen Nannochloropsis oculata (FN) and dried Spirulina platensis (DS), comparing to dried baker's yeast Saccharomyces cerevisiae (Y) in four treatment; alone for each diet and mixing between S. platensis + yeast and yeast: (FN, DS, DS+Y, and Y). The experiment was continued for 12 day in batch culture system with initial rotifer population 100/ind./ml. The lowest average in population and population growth rate were observed in rotifer fed on SD (122.90±43.38 Ind./ml and 0.137 ind./day, respectively), while the highest RFN and Rr were observed in Y (182.24±43.89 ind./ml and 0.569 ind./day), followed by DS + Y (166.00 ± 32.58 Ind./ml and 0.486 ind./day) and FN (130.09 ± 21.51 ind./ml and 0.251 ind./day, respectively). In general, Baker's yeast is cheap and readily available; in contrast, microalgae (fresh, freezed and dried) are laborious, time consuming and expensive. Baker's yeast S. cerevisiae has also been successfully used for rotifers with high population and population growth rate.