Tropic Marin REEF ACTIF -for vitality and colour in corals and reef clams. Tropic Marin REEF ACTIF performs a unique dual function as an adsorber and bacterial nutrient in saltwater aquariums. In doing this it assumes a central function as the link between inorganic nutrients and the biological population in the saltwater aquarium. Tropic Marin REEF ACTIF is suspended in the aquarium water where it bonds with both nutrients and water contaminants making them available as nutrients to bacteria and other animals that feed on dissolved organic material in the saltwater.