Algal scrubbers use live algae to do the “filtration.” Water is run over a wire mesh in a trough under bright lights, where algae is encouraged to grow. The growth of the algae removes some pollutants from the water. This is a controversial form of filtration for reefs and large marine ecosystems, invented by Dr. Adey at the Smithsonian. Some believe it is a complete filtration solution, others claim its use leads to poor water quality and algae growth in the tank as well. In freshwater planted aquariums, vigorous plant growth has been observed to beneficially consume excess dissolved nitrates.