The biofouling cause coorosion in marine environment or it is called as biological corrosion. The biological corrosion occur in the metal material both on coastal buildings, offshore buildings, port buildings and shipboard. One method to prevent the biological corrosion is ICAF (Impressed Current Anti-Fouling). The study of microalgae that cause biofouling was conducted in laboratory scale using simple ICAF system. The variables were the operating time of simple ICAF system, the strength of the electric current and the species of microalgae. The determination of cell number of microalgae was conducted using a neubauer improved Hemocytomete methode, while determination of the concentration of Cu ion using Atomic Absorption Spectrophotometry (AAS). The aim of the research was to determine of microalgae, Isochrysis galbana and Botryococcus sp, population reduction using ICAF system. Based on the results, the highest population reduction in Isochrysis galbana and Botryococcus sp was 77.5% and 50%, respectively. The highest concentration of Cu that was produced during operation of simple ICAF system reached 4.08 ± mg/L. In conclusion, ion Cu that was produced during operation simple ICAF system can reduce cell number of Isochrysis galbana and Botryococcus sp.