Premium research-grade low-ash Fluval Carbon is highly porous, providing large amounts of surface area for adsorbtion of impurities. It effectively removes heavy metals, odors, discolorations, organic contaminants and pollutants to leave your aquarium water crystal clear and sparkling. Fluval Carbon does not raise phosphate levels. For use in freshwater and marine environments. For filter models: 105, 205, 305, 405, FX5, 104, 204, 304, 404, 103, 203, 303, 403