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Thread: Old Algae Stains

  1. Back To Top    #1

    Join Date
    Jun 2016
    Prospect Heights, IL

    Old Algae Stains


    I have a 13000 gallon above ground pool with a vinyl liner. Last fall I got really busy with work and didn't keep up with the maintenance of the pool and it got stained from leaves and other debris that made its way to the bottom of the pool. It was getting late in the fall and cold and I cleaned it up as best as I could and closed it, but there were some stains that remained around the edges and bottom of the pool. I opened it 7 days ago and since then have vacuumed, shocked and tried to maintain proper chemical levels and remove the stains, but it's been tricky. I have shocked it twice and both times the free and total chlorine levels drop to near zero within 24-36 hours. For example, I shocked it Sunday night with 3lbs of pool life turboshock and by Tuesday I was reading zero on both. From what I have read, the loss of chlorine is due to low CYA levels, I did add 2 lbs of pool life stabilizer (powder through the skimmer) on Monday, but from what I have read, it takes a while to show up. As of today, I got these readings from test strips

    Total Hardness- 698
    Total Chlorine- 0
    Free Chlorine- 0
    pH- 7.6
    Total Alkalinity- 180
    CYA- 0-20 (the strips don't give exact measure, so this is a guess)

    My main goal is to get rid of the stains. They are organic because I dropped a chlorine tablet and after letting it sit for a while and rubbing it around the bottom, it showed to remove the green/yellow stain. Brushing the stains does not do anything. Can you please advise me on the best course of action? I have attached pictures of the stains for better reference and can get more exact water test, but I'd have to go to the pool store. Thank you for your help.


  2. Back To Top    #2
    Casey's Avatar
    Join Date
    Apr 2007
    SW PA

    Re: Old Algae Stains

    Welcome to TFP.

    First off, chlorine will get rid of the stains over time. Secondly, you need to start educating yourself in pool school by starting off with the ABC'S of Pool Water Chemistry. Follow up with test kits that are recommended. Tg e strips,are worthless and no one will address your test results if they arent from a recommended test kit. Finally, I encourage you to read How to SLAM your pool. It's not a one time addition of a product just because it says it's a,shock. You need to get to a high enough FC level tgat is in direct relationship with your CYA and keep it there until you lose no FC at night (OCLT). Until you do so, you will not remove the organic staining.

    The Pool School articles are there to help us enjoy trouble free pools. If you have any questions, we'll be here to help get them answered.
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    24' Sharkline Venture De Filter

  3. Back To Top    #3
    Mod Squad pooldv's Avatar
    Join Date
    Aug 2012
    DFW, TX

    Re: Old Algae Stains

    Welcome to TFP!

    Yes, elevated chlorine level and brushing will remove stains. The closer to shock level for your CYA the better, FC/CYA Chart. If you have active algae then it is time to SLAM. I use the TF-100 test kit and I've been buying mine from for years.

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