I live in Tampa Florida and have an EverGrain composite deck, which was installed years ago. I, like everyone else, get black mold stains. I have tried all the cheap products sold at Home Depot and Lowe's. Most just excessively bleach the color of the deck and don't get rid of the mold or last. I then tried Spray & Forget with no results. I called the company and they told me it would take up to 6 months to work. I told them I didn't want to wait till after Christmas for my deck to be clean or buy the company. I then tried Once and Done, which only lasted for a minute. Needless to say, I had previously used Corte Clean and you get what you pay for. I just ordered more and won't be again wasting my time or money with anything else.