Experiments were conducted to determine optimal salinity,temperature, nutrient level and CO2 supply required for achievingmaximal growth in culture of two commercially important microalgaeNannochloropsis gaditana L.M. Lubián and Dunaliella salina (Dunal)Teodoresco. Four different salinities, temperatures and nutrient levels(NaNO3) and two different CO2 levels were employed. The resultsindicate that maximum cell density was obtained in N. gaditana withcultures in 25 ppt salinity, 25°C temperature, 150 g/lit nutrient leveland 0.5 scfm CO2 supply. In the case of D. salina the highest celldensity was with 150 ppt salinity, 30°C temperature, 150 g/lit nutrientlevel and 2 scfm CO2 supply. Second set of experiments with acombination of optimal parameters resulted in significant increase incell density with both algae compared to routine culture conditions.