We have had this pool for twenty years, but after reading some posts I feel as though we've been doing it all wrong! I don't even know how to test for CYA. We thought the horrors of our Northeast winter were behind us until we opened our pool only to find the worst color water we've ever seen. I've gotten the water clear, but a 4-6 inch ring of brownish black stain remains just below the tile line. Any ideas of what this is? I suspect algae but it doesn't respond to the treatment. Do I use a whole bottle of multi- purpose algaecide every day? If so where can I get it without spending an arm and a leg? One bottle at my local shop is 27$. We also have never really used stabilizer, can anyone explain it in simpler terms than the article, I was never very good a chemistry. Thanks for any help!
Struggling in NY,