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Thread: black algae

  1. Back To Top    #1

    Join Date
    Sep 2015
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    black algae

    Ok, so another neighbour had asked me to take a look at his SWG pool based on the other neighbours chatting.....

    this guy has black algae spots in corners of the steps and in the grout of the tiles.

    He had replaced his salt cell back in January.

    today's reading were:
    FC 2.5
    CC 0
    CH 500
    TA 70
    CYA <20
    pH 7.8
    salt 2500

    He says that his cartridge filter is mucky green last time he cleaned it. The water looks clear and blue and his salt cell is at 100%.

    So, he knows to get the pH down to 7.5 and to get the salt up to 4000ppm for his machine. He can't remember the last time he added CYA but he thinks it was in January when he replaced the salt cell and Leslie's tested the water for him.

    Does he need to SLAM? What about the black algae - should this be dealt with before or after the SLAM? Adding CYA? Should we test the water like I did with the other neighbour's at 10ppm for 10 minutes and then when it's holding add the CYA?

    Why do I think the pool stores around here are sooooo bad???

    thanks
    26,390 gallons IG, Centex plaster, Hayward DE 4820 filter, Century Centurion B2859 pool pump motor.
    Booster pump for polaris 280
    Spa
    Built 1997

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    Texas Splash's Avatar
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    Re: black algae

    ha. You are right to be concerned about pool store testing. It's never as accurate as we would hope. So the numbers above are from your own test kit? If so, yes - I would say a SLAM is in order for your friend based on the last comment about his filter being green and a true SLAM was not done back then. During the SLAM, the spots could be manually scrubbed to break them loose or at the very least expose the surface so the higher FC can do its job. Make sure to turn-off the SWG now and have your friend hit HEB or Wal-Mart for some generic "regular" bleach (Bravo or Great Value). Use just bleach for the SLAM.

    Before the SLAM though, certainly make sure the pH is reduce to 7.2-7.5, and ensure the CYA is to at least 20. A CYA of 20 required an FC of 10; CYA of 30 required FC of 12. Make sure your friend knows the SLAM page inside & out. After the SLAM, then take that CYA up to 70 because it's way too low for a SWG pool. But do that after the SLAM has passed all 3 criteria, Hope that helps.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
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    Mod Squad YippeeSkippy's Avatar
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    Re: black algae

    Being that its Austin (hot, sunny) he definitely needs to up that CYA. Take it up to about 30 for the SLAM, then higher after done for the SWG. We recommend 70-80 CYA for SWG pools.
    He needs to turn the SWG off, add the salt (Taylor's K-1766 salt test is handy here) and let it get incorporated for 24 hours before turning the SWG back on. Or leave it off while he SLAMs using liquid chlorine.
    Tell him to monitor his filter pressure and clean it out via backwash as necessary. Running the higher chlorine through it will help kill off any algae in there too.

    Refer him to Pool School (up at the top of this page) and the directions for how to SLAM.
    Good job helping him Make sure he gets his own test kit....the TF-100 is my fave.

    Yip
    My Amazon Smile for November12K Fiberglass IG, Infinity 4000 automatic cover, SWCG, Hayward Sand Filter, Hayward 1.5 Pump, Doheny Discovery Robot, Savi Melody LED pool lights, outdoor speakers and other assorted doo-dads. Sundance Altamar Hot Tub.
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    Mod Squad kimkats's Avatar
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    Re: black algae

    You are going to be set up for life with pool party invites! LOL

    Kim
    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

  5. Back To Top    #5

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    Re: black algae

    Quote Originally Posted by kimkats View Post
    You are going to be set up for life with pool party invites! LOL

    Kim
    and beer!!!
    26,390 gallons IG, Centex plaster, Hayward DE 4820 filter, Century Centurion B2859 pool pump motor.
    Booster pump for polaris 280
    Spa
    Built 1997

  6. Back To Top    #6

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    Re: black algae

    Did you confirm that it is black algae as outlined in this link? Pool School - Black Algae

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    Re: black algae

    Quote Originally Posted by MarianParoo View Post
    Did you confirm that it is black algae as outlined in this link? Pool School - Black Algae
    Unfortunately, yes.

    I couldn't see the images in the post you've linked to and so I looked at some google images. That whole green smudge thing, I didn't do it on white paper just on my finger. And the pool was underchlorinated.
    26,390 gallons IG, Centex plaster, Hayward DE 4820 filter, Century Centurion B2859 pool pump motor.
    Booster pump for polaris 280
    Spa
    Built 1997

  8. Back To Top    #8

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    Re: black algae

    Don't raise the CYA too high yet, I'd leave it around 30 or 40 for the SLAM and then run the FC between 7 to 16 until the black algae is gone. The algae spots need to be brushed everyday with a stainless brush to expose it to the chlorine.

    Here is a link to black algae, Pool School - Black Algae.

    After the black algae has been defeated use the suggested levels for a saltwater pool.
    16k gal plaster with raised spa, Jandy DEV60 filter, 2 HP 2-speed SHPF Jandy Stealth pump
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