The effect of modified Zarrouk’s medium on the growth response of 6 different Spirulina strains was evaluated. Specific growth rate, doubling time, mean daily division rate, biomass, and chlorophyll-A contents were analyzed. Growth patterns of these strains were monitored continuously for 40 days. The results revealed significant differences in the growth parameters for different strains. S. platensis (SP-6) and S. platensis (CCMB) showed the maximum specific growth rates (µ = 6.1, µ = 5.8), doubling times (Td = 6.93, Td = 6.87), mean division rates (k = 0.27, k = 0.23) biomasses (5.1, 5.0 g/l) and chlorophyll A contents (78, 65 µg/ml) respectively, when compared with the other strains used in this study. Therefore, S. platensis (SP-6) and S. platensis (CCMB) strains can be suggested for large scale commercial cultivation with modified Zarrouk’s medium. This provides the basis of a low cost medium for cultivating Spirulina, which is known to be a promising microalgae with several benefits. © 2016, Walailak University. All rights reserved.