Kent Marine Phosphate Sponge for Aquariums Phosphate sponge is a ceramic medium which will adsorb phosphates quickly when placed directly in the water flow Works in fresh and saltwater aquariums or ponds Bring about 1-ppm of phosphate or silicates down to less than 0.05-ppm in a 120-gallon tank for every dry quart of medium Also absorb moisture for use as an air dryer for ozone and can be renewed over and over in moisture removal service For silicate to be removed, phosphates must first be removed; this product weighs 2-quart