The author characterizes effluent cleaning by algae that trapp a lot of residual pollution and, in comparison with vascular plants, their growth rate is higher, they can be cultivated during the whole year at artificial lightning, etc. Toxic metal bioaccumulation by microorganisms is characterized in moredetail, as well as sludge lagoon of the mechanical-chemical-biological waste water treatment plant of Slovnaft where Cladophora glomerata is used to eliminate residual pollution. The article is complemented by two graphs and a close-up photography of Cladophora glomerata.