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Thread: dark green algae staining bottom of pool?

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    Join Date
    May 2014
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    Menlo Park, CA
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    dark green algae staining bottom of pool?

    photo.jpgHi. My water is clear but I have what looks like algae staining the bottom of my pool. Please see attached photo. Since my water is clear, do you recommend a complete SLAM or is there another alternative? And if I do SLAM it, what is the max Cl level that is considered safe for swimming?

    Here are my test results:
    pH 7.3
    TA 90
    Ca 250
    Cl 3
    CYA 32

    Taylor K2005 test kit.

    Updated: I just swept the pool. There is a small grey/green/brown cloud that comes off the bottom when I sweep it.

    thx!
    Last edited by CADIYPool; 09-20-2014 at 08:17 PM. Reason: Added more info
    35,000 gal plaster pool
    Trichlor tablets in auto-feeder
    Jandy cartridge filter and heater
    Delta UV light sanitizer
    Taylor K 2005 test kit

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    Mod Squad jblizzle's Avatar
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    Re: dark green algae staining bottom of pool?

    Sounds like it could be algae so you should follow the ShockLevelAndMAINTAIN Process. It is safe to swim up to shock level, see the FC/CYA Chart, although best to focus on the SLAM.

    One issue is that you do not have the appropriate chlorine test. You need to add the FAS-DPD Chlorine Test to your kit to have the equivalent of the recommended K-2006.
    Jason, TFP Moderator
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    Re: dark green algae staining bottom of pool?

    Thanks. The new test kit is on order. How do I know if it is mustard algae and therefore requires the higher chlorine level?
    35,000 gal plaster pool
    Trichlor tablets in auto-feeder
    Jandy cartridge filter and heater
    Delta UV light sanitizer
    Taylor K 2005 test kit

  4. Back To Top    #4
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Location
    Tucson, AZ
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    37,389

    Re: dark green algae staining bottom of pool?

    Read the mustard algae article in Pool School. Does not sound like mustard algae to me. Besides you follow the normal SLAM process either way.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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