Once I published this book, I had the opportunity to go to different sites and listen to chats on writings and articles done by "ghost writers" for people who mainly sell newsletters and ebooks.  A lady who has written close to 300 ebooks, by her own admission, is bidding on one for pool maintenance and chemistry.  Her qualifications are that she wrote an ebook on ponds for  homeowners.  She brags that it can't be that difficult.  The moral to this story is to make sure the advice you get is from an actual professional or you may destroy your pool surface and equipment or cause a serious issue with the health and safety to the ones using the pool or spa.  Remember, we put poisons in water.  Not knowing what you are doing can be very dangerous.