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Thread: Possible Black Algea?

  1. Back To Top    #1

    Join Date
    May 2012
    Location
    Houston
    Posts
    6

    Possible Black Algea?

    Have black/dark grey splotches over most of the bottom of the pool which first appeared about 2 -3 months ago. Can't really say that a chlorine puck test makes a lot of difference when putting one on top of it for a while. Just got my TF100 kit and have run the numbers. As it has rained a lot over the last couple of weeks (Houston, TX) and has been hard to maintain balances.

    Current tests are:

    salt 2980
    FC 8.0
    PH 8.5
    TA 80
    CH 220
    CYA 20
    TEMP 84 DEG F
    CSI .65

    Just put in a qt of 31.48% Muratic due to high PH above.

    Have 2 hp Jandy Stealth pump and pool is 6 yrs old.

    Attached is a copy of the results from the calculator.
    Noticed from other posts that you want the OCLT, what is this?

    Havenít had a problem keeping FC at proper levels, actually they seem to run high for a long time (i.e. several days) after shocking. Am running the Jandy Purelink SWG at 75% - 85% for 5 hrs / day.

    Am adjusting for high PH (1 qt. 31.48% Muratic), but once this is done what recommendations for the shocking for the possible algae? Or could this be algae or something else?[attachment=07mnak1c]poolcalc.JPG[/attachment7mnak1c]
    Attached Images Attached Images
    Paul R. Powers

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Possible Black Algea?

    Welcome to TFP!

    Your PH is way too high. You should never allow PH to go above 8.0. Bring PH down to around 7.5 right away. CYA is also a little low, but that isn't as time critical as lowering the PH. High PH will bring on metal stains, which is what I think you probably have.

    The first step on the stains is to figure out for sure if they are black algae or metal stains. Black algae will feel slimy, and a little scraped off with you finger nail and smudged on a piece of paper will look green. Metal stains will feel like plaster, perhaps a little smoother, and will be completely unaffected by a fingernail.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. Back To Top    #3

    Join Date
    May 2012
    Location
    Houston
    Posts
    6

    Re: Possible Black Algea?

    Sounds like metal stains. The feel is not slimy nor is there any residue when scrapping, instead feels like plaster.

    Will get the PH down, this has been one of my ongoing problems with pool is to keep the PH down.

    Thanks
    Paul R. Powers

  4. Back To Top    #4
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Possible Black Algea?

    Bringing up the CYA level will significantly reduce the rate of PH drift. You can also allow the TA to go down to around 60, which will also slow it down.

    Try placing a vitamin C tablet on one of the stains for 30 seconds or a minute and see if that has any effect.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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