Seachem SeaGel 1 Liter. SeaGel is a blend of MatrixCarbon and PhosGuard. MatrixCarbon is an ultracapacity carbon for the removal of organic and color impurities. PhosGuard is a powerful remover of phosphate, silicate, toxic metals, and acids. Both components are bead shaped for optimum water flow characteristics and penetration. The components enhance each other and are ideal for reef and marine use. May also be used in freshwater that is not phosphate buffered. This product is sold by volume. Cited weight is minimal weight. DIRECTIONS: Use 500 mL for each 300450 L (80120 gallons*). Use in a filter bag. Rinse in freshwater before use. Use caution, since product will fizz and heat on initial wetting. SeaGel will function 34 months. May also be used in freshwater that is not phosphate buffered.