A high magnesium reactor media. ARMTM Extra Coarse is still a complete reactor media containing not only calcium and carbonate, but essential trace elements as well. ARMTM Extra Coarse contains: 275200 ppm Calcium, 590000 ppm Carbonate, 2200 ppm Strontium, and 2000 ppm Magnesium. Works with many Tunze, Precision Marine, Korallin, Schuran, Coralife, Knop, Coral Vue, Vorex , Octopus, and Pacific Coast reactors.