what causes a salt water pool to turn green
There are three causes of green pool water. The first is a lack of chlorine. Without chlorine the pool water will quickly start to grow algae and turn green. Water without chlorine, especially if it has an algae bloom, is unsafe to swim in, and can be a breeding ground for mosquitoes and other insects. The second thing that causes pool water to look green (or yellow) is pollen.
The last cause of green water in pool water is metals, usually copper, that have oxidized. Metals can be introduced through source water, from some cheap algaecides, or, if the water is acidic, from the metal components of the pool, most commonly from copper heater elements.