The Kent Marine Phosphate Sponge is a ceramic medium which will absorb phosphates quickly (within hours) when placed directly in the water flow. Works in fresh and saltwater aquariums or ponds to bring about 1.0 ppm of phosphate or silicates down to less than .05 ppm in a 120 gallon tank for every dry quart of medium. For silicate to be removed, phosphates must first be removed. Beads are cracked to expose more surface area and increase efficiency. This product will not release soluble aluminum compounds into your aquarium, causing negative reactions from your inverts, as competing products may. Will also absorb moisture for use as an air dryer for ozone, and can be renewed over and over in moisture removal service.