Three fresh water microalgal isolates [Phormidium ambiguum (Cyanobacterium), Pseudochlorococcum typicum and Scenedesmus quadricauda var. quadrispina (Chlorophyta)] were tested for tolerance and removal of mercury (Hg²⁺), lead (Pb²⁺) and cadmium (Cd²⁺) in aqueous solutions as a single metal species at conc. 5-100 mg / L under controlled laboratory conditions. The obtained results showed that Hg²⁺ was the most toxic of the three metal ions to the test algae even at low concentration (