Boyd Enterprises Chemi-Pure Elite can be used with all water types as a chemical absorption filter and ion generator and exchange unit to positively keep pH at a perfect constant level. Also fantastic for use with African Cichlids and Discus! Chemi-pure Elite formula now contains ferric oxide, that helps remove slime and PO4 (phosphates), giving your coral and fish a healthy environment to grow and live. 6.5 oz. Treats 25 gallons. Replace every three months. Pre-packaged in a nylon filter bag.