The live food (phytoplankton and zooplankton) is a very important food source in fish farming, particularly for early larval stages. Therefore, the present study was carried out to determine the consumption rate (grazing (G) and ingestion (I) rates) of three zooplankton species of different size, Brachionus plicatilis, Acanthocyclops trajani, and Heterocypris salina. Five different concentrations (10, 20, 30, 40 and 50 x10⁴ cells/ml) of the most common cultured phytoplankton species (Chlorella vulgaris) were utilized as fed for these species. The optimal concentration of the green algae that nourish the zooplankton species with minimum leftover that could affect the water quality was determined. The results revealed that grazing and ingestion rates of  B.  Plicatilis  and H. salina showed linear regression with algal concentrations (p < 0.008;  R²=0.72 and 0.82,) and (p <0.001; R²= 0.969 and 0.964), respectively.Their consumption rates values increased markedly with increasing the concentration of C. vulgaris. On the other hand, the consumption rate of A. trajani were independent of algal concentrations (p ≥ 0.09 and 0.07; R²= 0.07 and 0.05, respectively), and reached their maximum values at 30x 10⁴ cell /ml. The study concluded that C. vulgaris  is a suitable food for B. Plicatilis   and H. salina while it is  not  for  A. trajani, where its feeding behaviour still needs more in-depth studies.