Possible effects of various iron concentrations on the growth of green algae, Ankistrodesmus falcatus, were studied at Inland Waters Aquaculture Research Center, in Bandar Anzali, Guilan Province. The algae was grown under laboratory conditions with a water temperature of 25±2°C and light intensity of 3500±350lux for 96 hours at 6 concentra tions of Fe in triplicates, using standard Zander culture medium (Z-8±N) as control. The amount of Fe absorption was measured using spectrophotometry at 750nm, and the number of algal cells at the beginning and final stages were counted, using Toma slide. Maximum growth of Ankistrodesmus falcatus was observed at Fe concentrations of 0.0005 g/l, when the concentration of the element in the control group (Z-8:tN) was O.00019g/l.It was shown that Fe concentrations higher or lower than O.0005g/l had negative effects on the algal growth