The marine microalga Tetraselmis striata was cultivated in drilling waters obtained from the commercial fish farm Plagton S.A. (western Greece). The waters were supplemented with the fertilizer Nutri-Leef 30-10-10 of which the optimum growth quantity was found to be 0.2 g L-1. The effect of different pH and temperature values on biomass and lipid yields was examined. The optimum growth conditions were found to be pH 8 and temperature 25 oC and lead to maximum biomass productivity of 79.8 mg L-1 d-1 and a specific growth rate of 0.16 d-1. The biomass of Tetraselmis produced in the optimum growth conditions was rich in bioactive compounds and especially crude protein (51.3%), while analysis of the fatty acids revealed high percentages (up to 14%) of eicosapentaenoic acid (EPA).