Microalgae are the natural feeds of many aquaculture species, and are the basis of the natural food chains on which sush species de­pend in the wild. The algae were grown in batches using successively larger containers. A cell density, chlorophyll and dry biomass were ob­tained from the final 4-day culture of 6.5 X 10⁶ cells/ml, 4.77 mg /1 & 0.75 g/1 for Chlorelle vulgaris, and 5.4 X 10⁶ cells/ml, 4.96 mg/I & 0.82 g/1 for Scenedesmus bijuga, respectively. The mass production costs for outdoor tanks of microalgae were about LE 66.38/kg dry biomass and of LE 40.53/ton of live algae (US$ 1.00 = 3.35 LE Egypt.). In the present study, the cost of labor (39.48%), electricity- (25.94%), nutrients (8.11%) and mixing (26.47%) of the total production costs were studied. The multi-step method used in the mass culture of microalagae in this investigation minimized the production costs.