The Theiling Rollermat is like a filter sock, except that it filters detritus out of the water column by passing it through filter paper off of a long roll. As the filter paper clogs, the water level in the cleaner rises. When the water rises it activates a float switch that causes the roll of paper to rotate, exposing fresh new filter material. This method results in a filter that is smaller and less expensive than models that rely on a mechanical water wheel. Connect with us on Facebook: Check out our pics on Instagram: