We purchased a home with a 20 x 40 salt water pool 3.5 years ago. Had a company managing it up until February when they decided to sell out contract to a company without telling us and then our pool went downhill in the 3 weeks when we found out (noticed pool tiles were covered in green algae). Now, we are trying to manage it. Dealing with some black algae spots now...fun! I've been trying to learn as much as I can through reading your forums.