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Thread: Algae? Stain? with pictures

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    Algae? Stain? with pictures

    Recently, I noticed some brown spots on the floor of my pool. There a several of them, but not many.
    They can't be brushed off, and do not grow (yet) either.
    I have shocked my pool with FC15-17 last Sunday, and overnight is less than 0.5.
    FC: 5
    CC: 0
    pH: 7.6
    CH: 260
    CYA: 40 (just replaced 2/3 water last Saturday.)
    Borate: 0 (i guess, the test strips will be delivered tomorrow)

    Any ideas about what they are and how to remove them?

    Thank you in advance~
    Attached Images Attached Images

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    Join Date
    Feb 2008
    Flower Mound, TX

    Re: Algae? Stain? with pictures

    Looks like metal stains. Here's how you can tell. Take a vitamin C tablet and scratch it on the stain. If it lightens, it's metal staining. If it doesn't, try taking a chlorine tablet and setting it on the spot for about 20 or 30 minutes. If it goes away then, it's organic and will disappear with proper chlorination; faster if you shock your pool.
    10K gallon IG gunite with waterfall; Pentair CC320P filter; WhisperFlo 2 HP pump
    TF Test Kits - Pool Math - Pool School
    "It depends."- JohnT

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    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: Algae? Stain? with pictures

    Very good chance those are rust. Even the tiniest piece of steel can leave a mark. I had a few freckles after I had a fence replaced.

    Solution: Vitamin C tablets. I just bought the cheapest store brand. I smasked them into about quarters and stuck them in a nylon with some smooth rocks and tied a string to it. Then I set it on the spot. It might take some nudging with the pool brush to get it on the right spot. I just left it there overnight. Done.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Algae? Stain? with pictures

    thank you so much for you quick reply!
    I will try Vitamin C, and report results tomorrow

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