The first year I used solar cover I also used the trichlor method. The FC level wasn't higher than 2, according to the OTO test which I used at that "pre-historic" pool period. The cover didn’t show any sign of decay. The second year I used the BBB method, and according to my CYA level I had to maintain FC level between 5 and 7. At the end of the season I saw that many “diamonds” fell apart. Does anyone know how resistant is the solar cover to FC? What is considered the highest level of FC that it can endure?