The effect of ammonium and nitrate, as the sole source of nitrogen (1, 2, 4, 8, 16 mM) and in mixtures (4+1, 4+2, 4+4, 4+8, and 4+16 mM, nitrate+ammonium), on the productivity of biomass, lipids, carbohydrates, proteins and total pigments of S. dimorphus was determined. The experiments were conducted in 450 mL photobioreactors with BG11 medium. S. dimorphus showed growth under all nitrate concentrations tested with the highest productivity at 4 mM. However, there was no growth in media amended with only ammonium. The nitrate and ammonium mixture (4+1 mM) increased by 38.37% of the biomass productivity, compared to nitrate 4 mM. This combination also increased lipid, carbohydrate, and total pigment productivity by 65%, 69%, and 51.8%, respectively. Nitrate was suitable to produce S. dimorphus biomass. Unexpectedly, ammonium in any concentration inhibited S. dimorphus growth, nevertheless ammonium 1mM with nitrate 4 mM significantly increased productivities.