Red Sea Reef Spec Carbon, 500 ml, is a great choice for Red Sea Max marine & reef aquariums, as well as any other marine or reef aquarium. The Red Sea Reef Spec Carbon's granule size and its micro/macro porous structure ensures a very high total adsorption capacity and rapid extraction of the specific organic pollutants that are found in Reef aquariums. It has extremely low phosphate leaching and minimal ash content while also not affecting the pH of aquarium water. It needs replacing less frequently than carbons that are not reef-specific or are of a lower quality and represents an effective, cost-efficient solution for providing the very best water quality in marine & reef aquariums.