The Professional Phosphate Reducer Pad quickly reduces phosphate buildup in fresh water & saltwater aquariums, aquaculture, terrariums & hydroponic systems. Phosphate buildup creates algae blooms, which depletes oxygen, creating a toxic environment for inhabitants. The pad also traps micro & macro organic particles, debris & excess fish food in hang-on filters, prefilter boxes, custom sumps/refugiums and more. The cut to fit pad is extra thick and safe for freshwater & marine aquariums Increases the well-being of your aquaria pets by reducing the risk of disease and stress. Measures 18 inches by 10 inches.