High quality activated carbon especially developed for salt water tanks. You will see the difference significantly on your corals. Put it in a mesh bag in a passively flown filter bypass or in a nylon stocking on top of the ZEOvit in the ZEOvit filter. Rinse the carbon briefly with hot tap water before use. The result is a better polyp extension. It adsorbs toxins, toxic compounds and yellowing compounds and also proteins. Keeps your tank water crystal clear. Use 1 L Korallenzucht activated carbon for 250 gallons/1000L water. Completely replace every 30 days.