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Thread: Algae in Rocks above pool water line

  1. Back To Top    #1

    Join Date
    Aug 2012
    Missouri City, TX

    Algae in Rocks above pool water line

    I don't have any pictures with me right now, I'll try and take a few tonight to post.

    We have a stacked flagstone wall on one of the sides of our rectangular shaped pool. Last night, while swimming with the kids, I saw some green algae inbetween a few of the rocks above the wall. This is an area about 2-3 inches above the pool waterline, but a place where the rocks get wet from splashing.

    My test results from last night:

    FC: 5
    CC: 0.5
    TA: 80
    pH: 7.5
    CH: 660 (need to test my fill water - has been slowly rising from around 220 last fall right after we filled the pool)
    CYA: 45 - 50 range (just a little below the 50 mark)

    I use a stenner pump to inject chlorine, right now it runs for 45 minutes in the morning around 10am and then another 15 minutes around 6pm. I am thinking of switching that up as I have read on here that it is generally a good idea to add the chlorine in the evening.

    The pool gets full sun from about 10am to 5pm. The water is clear. I am in the process of trying to lower the TA as the pH does creep up and I typically need to add 20oz of acid every other day. The pool was built last August, and has a rock overflow spa and a bubbler on a small sun deck so that contributes to the rising pH as well.

    Any ideas on the algae above the waterline in the rocks. I am thinking of just using a nylon brush and some bleach to clean it, of course that will flush the alge into the pool. I don't think I have anything wrong with the pool water as it is clear and I keep the FC in range.

    20,000 IG WetEdge Satin Matrix Northshore Plum, Filled 8/24/12

  2. Back To Top    #2
    Mod Squad Patrick_B's Avatar
    Join Date
    Jun 2011

    Re: Algae in Rocks above pool water line

    Pool FC wont make a difference on that area, so that isn't the problem. You will have to stay up with it like you mention with bleach and mechanical removal. Your rising calcium could be a problem though, and it is too high. I would test the fill water for sure. Hopefully it is coming from that, and not all from your pool finish. Did you follow their start up procedure after filling?
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