I went to my brothers pool after he left it unattended for a week, and it was green. The outdoor temperatures were over 105 degrees. The algae was thick, so I put in a gallon of ammonia, bought at WalMart for $2, and 4 gallons of chlorine. The next day the pool was blue, no more algae. The filter had to be cleaned because of the dead algae, that is a must. Also the chlorine must be checked every other day, for the ammonia and chlorine work together, the combination uses the chlorine to kill the algae. The use of the pool is on hold for a few days, but the end result is an algae free pool. Where the temperatures are high in the desert, the chemicals are used quickly. A floater chlorine container> with chlorine tabs inside, helps to keep the residual up and the water clear. Enjoy the pool.