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Thread: Stubborn Black Algae spots

  1. Back To Top    #1

    Join Date
    Jun 2015
    Location
    houston, TX
    Posts
    7

    Stubborn Black Algae spots

    Experienced guys please suggest a solution for black algae as appears in pictures below. I have this black algae spots for about a month or so. I have tried to scrub it off but no luck.
    have done SLAM two weeks ago but no luck. Below is the current water analysis.

    Total CL - 1.5
    Free CL - 1.3
    PH - 8.1
    Tot Alk - 73
    Adj. Tot Alk - 52
    Hardness - 230
    Salt - 3200



    fr_738.jpgfr_737.jpg
    16k gal plaster with raised spa, Hayward Swimclear 5020 filter, 2 HP hayward pump
    Hayward Aqua Rite T-15 SWCG, Hayward 400k BTU NG heater

  2. Back To Top    #2
    BoDarville's Avatar
    Join Date
    Jun 2012
    Location
    DFW, Texas
    Posts
    3,840

    Re: Stubborn Black Algae spots

    Welcome to TFP!

    While other forms of algae are primarily removed with SLAM-level chlorine levels, the key to removing black algae is brushing - elevated chlorine levels alone will not be effective on black algae. You may have to go with a stainless steel brush on a plaster surface in order to knock off the algae’s protective coating so that the chlorine can attack the algae itself. As for chlorine the chlorine level, maintain it between the high end of the recommended “Normal” range and the Shock (SLAM) level according to your pool’s CYA level. For example, if your pool’s CYA is 40, the high end of the “Normal” FC range is 7 ppm and the Shock/SLAM level is 16 ppm. In this case, you would maintain it between 7 and 16 ppm. I do not see a CYA level in your test results. You will need to know that parameter in order to determine your targets and dose chlorine properly.

    For more info, see Black Algae
    Gold Supporter, TFP Lifetime Supporter, 26,680 gal Plaster IGP 3.5 - 10' depth / Attached Waterfall Spa, Manually Chlorinated, Triton Sand Filter, 1.5 HP * 1.1 SF = 1.65 SFHP 1-speed Pentair WhisperFlo WF-26 Pump, 400K BTU NG Teledyne Laars Series One Heater, Polaris 360, Test Kit Comparison, Chlorine/CYA Chart, SLAMing Your Pool, OCLT
    A good test kit is an investment, not an expense.

  3. Back To Top    #3

    Join Date
    Jun 2015
    Location
    houston, TX
    Posts
    7

    Re: Stubborn Black Algae spots

    Thanks for the reply ! I will try to follow that.
    Btw CYA is 70.


    16k gal plaster with raised spa, Hayward Swimclear 5020 filter, 2 HP hayward pump
    Hayward Aqua Rite T-15 SWCG, Hayward 400k BTU NG heater

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