Abobe ground pool water is green?

Green pool water is caused by algae growth. When chlorine levels drop below 1-parts-per-million, algae will begin to grow. To get rid of the algae, turn on the pump so chemicals will circulate through the water. Correct the pH level of the water by adding an acid or a base to bring the pH level to a 7 or 8. Clean any debris out of the pool. With a nylon brush scrub the pool, breaking up the algae. Add shock to the pool, and continue running the pump throughout the cleaning process. The water will be cloudy when the shock is first added, but will soon begin to clear. Once the water is clear, vacuum the algae from the pool.