Macronutrient requirements of the cyanobacterium Westiellopsis MKU 157 were optimized for higher biomass production by using a factorial experimental design, which saved time as compared with classical methods. The most suitable medium found from the design matrix experiments is: NaNO3, 750; K2HPO4, 120; MgSO4 0.037 CaCl2, 0.014; Fe++, 0.018; EDTA, 0.0005; and Na2CO3, 0.060 mg/l with A5 (micronutrients) medium. The growth rate was further enhanced (30%) by adjusting the pH of the medium. The optimized medium (OM) was also compared with BG 11 in a 20 l low-cost bioreactor.