Unique is truly four chemicals in one. This product is available in a quart size and removes iron, stain, rust, scum, scale, foam, and clears cloudy water. If your pool water has a high mineral content or your fill water is from a well then this chemical is a must. I personally recommend using 2-4 quarts each spring during the startup of your pool. Preventative maintenance typically requires another 1-2 quarts per swimming season.