Water discoloration is often caused by metals in pool and spa water. When your pool is termed “green,” people often think it is caused by algae, which is an aquatic plant. If you are shocking your pool and the green just will not go away, you may not be dealing with algae at all. In many cases, the green tint of the water is something quite different and actually caused by metals. Even when water is discolored it can be said to be “stained” by metals. When water has already turned color, metals cannot show up accurately on a metal test. Therefore this problem often goes undetected. Fix that green pool with Natural Chemistry’s Stainfree or Stainfree Extra Strength products and Metalfree for pools or Spa Stain & Scale™ and Spa Metalfree for spas.