Hello all. Just wanna say I enjoy reading all the posts and all of the great information you share. I'm hoping I can get some assistance. My first time owning a pool and I just had it installed in June. I have the Perma Salt system (I know, I know... Why? After reading other posts) and the pool is 21ft, above ground, and 52 inches high. I'd say about a month in, a stain started to develop on the bottom, I would shock and it would go away. Then after a couple of days it would return, well now here we are today and the original stain is a bigger stain and there are medium and small stains running along a path. I've used whole bottles of Proteam black magic algae killer, some commercial black algae kill ( as per my local pool store), multiples bags of shock all in the past week n a half and while the stains have lightened a bit they are still there and really frustrating me. I hope someone can please shine some light onto my gloomy self and please make me not regret getting this pool. My apologies for such a long post, just had a lot to say. Thank u again.