We opened our pool with a pretty low CYA level this year and by the end of June our CYA had dropped to 20. Since we were leaving for a week, we turned on our auto-chlorinator. We've continued to use it since July and just turned it off last week because it's nearing a level of 50. (That's not a problem for us right now because we'll be closing our pool in two weeks.) Once we started using the chlorinator, we raised our TA to 100, like the "Recommended Levels" chart says, since our pool is vinyl.
We battle yellow mustard algae, so we always keep our FC on the higher end. We had to shock it two weeks ago because of heavy pool use & the FC level has dropped very slowly because the water is cold & we've had the solar cover on most of the time. We uncover the pool 1/2 way every fourth day to run the Polaris for approx. 3 hours. We did have the cover completely off of the pool all day on Sunday.
Today, the water is light green & we clearly have green algae growing on the bottom. I don't think it's mustard algae, because when we have mustard algae it always grows up the slanted side on the deep end (along with everywhere else). In addition, the mustard algae never looks bright green like what I'm seeing today.
All of my readings look decent, except PH needs to be raised. I re-tested THREE times, because I don't see how I can have algae with these test results:
Could low PH have been the cause of the algae? If not, I'd assume that I don't actually have algae, but the water is visibly light green and the algae is pretty thick in spots on the bottom. In addition, when I use my fingers to scrub the algae that is visible on our white steps (and on the white steps on our ladder) I really have to rub to remove it. It doesn't just drift away easily into the water like dirt and pollen do. What am I missing?