Top-down control is an important type of interspecies interactions in food webs. It is especially important for aquatic ecosystems. Phytoplankton grazers contribute to the top-down control of phytoplankton populations. The paper is focused on the role of benthic filter feeders in the control of plankton populations as a result of water filtering and the removal of cells of plankton from the water column. New data on the inhibitory effects of surfactants and detergents on benthic filter-feeders (Unio tumidus, U. pictorum, Mytilus galloprovincialis, M. edulis and Crassostrea gigas) are presented and discussed. Importance and efficiency of that approach to the problems of eutrophication and water self-purification is pointed out. Chemical pollution may pose a threat to the natural top-down control of phytoplankton and water self-purification process. The latter is considered an important prerequisite for sustainable use of aquatic resources.