Thank you so much for the info- I have enjoyed reading all of your posts. They are always filled with good info. Someone should publish a book with all of these tidbits of info in it. I certainly would buy it! I am not a new pool owner- we have had this pool for 7 years- we only started having problems about a year ago a stuborn algae problem and trouble getting our readings tohold steady-I blamed a lot of things for this porblem and I listened to our pool store and I think we have made the problem much worse. I am still going to research SWG and if you know of any that you like more than others I would appreciate the info- Again thanks for all you knowledge- I am going to use bleach!