above ground pool of about 650gallons . When should I treat the water? How often?
When and how often to treat the water is dependent on several factors - bather load, organic load, weather, etc. The best thing to do is test the water 2 to 3 times a week and then adjust as necessary. Some weeks you will adjust very little, if at all. Others you will adjust more. However, testing and making small adjustments will save you money over the season vs. letting the pool go and having a problem that requires a lot more chemical treatment.