A regenerable, bead shaped resin which safely removes heavy metals. Safe for use in all aquatic systems. Removes copper, lead, mercury and other heavy metals from marine and freshwater aquariums. Also works well to remove metals from tap water. Contains special form macroporous cation exchange resins. Regenerable over and over again. Light beads turn a slight blue or gray, indicating exhaustion and need for regeneration. Resin life is about 2 years of service. 250 ml size.