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Thread: HELP Black algae spreading!

  1. Back To Top    #1

    Join Date
    Aug 2010
    Location
    Lake Jackson, TX
    Posts
    130

    HELP Black algae spreading!

    I have a growing black algae problem. I posted pictures in an earlier post (June 20th). At that time there were not a lot of spots and they were confined to the deep end about 5 feet down. I was keeping the FC at 7-10 during that time, and yes I messed up a couple of times and let the FC drop below the 7 minimum, but never longer than a day.

    Since then I have tried to keep the FC to at least 10. I have tried the vitamin c with no effect and the chlorine tablet with no effect, although it was difficult to do anything 5 feet down. I bought a wire brush and have brushed some but it doesn't seem to do anything.

    Now, the black spots have spread. The original area is 2-3 times as wide and longer and there are mo0re spots in other areas.

    So, what do I have to do to get rid of this BA? How high does the FC have to be and for how long? Does the pH matter?

    Thanks all.


    FC 12.5
    CC 0
    TA 190
    CH 410
    pH 7.8
    CYA 80-85
    TEMP 89
    25000 gal IG gunite plaster. Built in spa, built 1984.
    48 SF Hayward DE-4800 filter
    1 hp Hayward super pump
    3/4 hp Polaris PB-4 booster pump, Polaris 380
    Taylor K-2006 test kit

  2. Back To Top    #2

    Join Date
    Feb 2008
    Location
    Denton, TX
    Posts
    5,061

    Re: HELP Black algae spreading!

    Best thing to do is bring your pool to shock level and brush the spots with a stiff brush as often as you can. BA is very tenacious and is one of the toughest things to rid yourself of. Unfortunately, vitamin C will only lighten a metal stain. It won't do anything to black algae. The pH should be as close to 7.2 as possible while shocking.

  3. Back To Top    #3
    Butterfly's Avatar
    Join Date
    May 2007
    Location
    South Carolina
    Posts
    10,045

    Re: HELP Black algae spreading!

    You will have a hard time shocking with a CYA of about 85. I suggest you lower it to about 50 thru a drain/refill dance. That will lower your shock level from about 32 to about 20.

    You will need to maintain shock level and brush the BA daily with the algae brush while at shock level. Brushing knocks the heads off and allows the chlorine to get in and kill it.

    Maintain the shock level until it is gone. Then, for the rest of this season, I suggest you maintain your FC at Target level and don't let it drop down to the minimum for your CYA. BA can be a buggar to get rid of and keep away. So be diligent.

    Then, once the BA is gone and you are maintaining, you should brush the pool at least weekly with a SS/wire brush.
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  4. Back To Top    #4

    Join Date
    Aug 2010
    Location
    Lake Jackson, TX
    Posts
    130

    Re: HELP Black algae spreading!

    I forgot to add, I dug into a few of the spots and there was definitely green roots going into the plaster. I was hoping to maintain until fall and then deal with it but it's getting out of control.
    25000 gal IG gunite plaster. Built in spa, built 1984.
    48 SF Hayward DE-4800 filter
    1 hp Hayward super pump
    3/4 hp Polaris PB-4 booster pump, Polaris 380
    Taylor K-2006 test kit

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