The green phytoplankton alga Chlorella sp. is normally used in mariculture for human food, and for culturing zooplanktons in marine fish hatchery. In a microalgal culture under illuminated conditions, the production rate of cells depends on the distribution of light intensity and growth rate of cells (1). The aim of the research was to establish optimal light intensity in order to access maximal abundance of Chlorella sp. in the shortest time.