API Prevent Algae removes phosphate and silicate. This clears cloudy water which are caused by these factors. Enhances the growth of hard and soft corals in saltwater and removes compounds that inhibit plant growth in freshwater. Designed to perfectly fit the Nexx filter One box contains 2 pouches - each pouch lasts 2 months Directions: 1. Rinse pouch under tap water for several minutes to remvoe dust and activate the prevent algae. 2. The cartridge does not need to rinse clear 3. Fit to your Nexx FIlter