Seagel is an efficient blend of matrix carbon and phosguard. Seagel removes organic and color impurities, phosphates, silicates, toxic metals and acids. Both components are bead shaped for optimum water flow characteristics. Seagel is ideal for reef and marine aquarium use, particularly for algae control. It may also be used in freshwater that is not phosphate buffered. A 250 ml bottle will treat 40-60 gallons for 3 to 4 months. Marine or freshwater use.