Green pools are not usable pools. Many pools are green and its due to formation of algae. Algae can form a pool without proper pool service. Algae is unsightly and very troublesome to most pool service companies or weekend do-it-your-self weekend warriors. Many factors can lead to algae and if not treated properly can lead to extra expenses. Shock treatments and algaezide are available for immediate impact.
Chlorine is a chemical added to swimming pools to kill bacteria that can build up over time and lead to a discoloration of the water. Green water is most often a sign of algae, not necessarily bacteria, but different pools have different bacteria that can affect the water.
Not all water-color issues are the fault of the water itself. For example, a filter system that isn’t working properly won’t strain out the surface algae and other debris. If left to stagnate, your pool will become a breeding ground for mold, algae and other fungi that will eventually change the color of the water.
Algae thrives in warm, humid temperatures. Normal chlorine may not be enough to counter the buildup of algae within a pool, but there are special algaecides sold which are specifically designed to work against those extra-tough algae!
The best remedy for a discolored pool is regular maintenance! If the pool has been neglected for several months, consider employing a pool professional to drain and chlorine/acid wash the walls.