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.