Fluval UltraGrade Carbon has been specifically manufactured for aquarium filtration of fresh and marine environments. The internal cell matric is able to adsorb most liquefied impurities and dyes present in aquarium water. Each granule of Fluval UltraGrade Carbon is permeated with numerous pores opening to cell structures that allow rapid diffusion of adsirbed waste material. Fluval UltraGrade Carbon consists of fine, pure carbon granules; it contains no phosphates and will not change pH of aquarium water