Activated Carbon is the most commonly used media to purify water. It is the same product used in household filtration systems to purify drinking water. It is also effective for removal of chlorine and moderately effective for removal of some heavy metals. Metals that are bound to organic molecules will also be removed by AC. These include urine, dyes and impurities. This action creates sparkling clean water in aquariums. The large internal surface area also provides numerous points for important bacterial colonies to form and thrive. Fluoride, chloride, nitrate, hardness (calcium and magnesium) and most ions are not removed by AC to any significant degree. This product is processed for effective aquarium filtration in fresh and salt-water environments and should never be mistaken as bone charcoal, which is of inferior quality. Activated Carbon should be replaced every 6 – 8 weeks. Carbon should always be removed during medication.