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Thread: Black algae spots stubborn to remove

  1. Back To Top    #1

    Join Date
    Jul 2016

    Black algae spots stubborn to remove

    FC 2.5
    CC 0.5
    CH 250
    TA 125
    CYA 60
    The pool water is clear no issues but have stubborn black algae spots which appears in two layers. The top "biofilm" layer is shiny which (steel) brushes off easy leaving the more stubborn layer underneath the shiny layer which is embedded into gunnite floors or walls. What is the alternative to attack the stubborn layer, as is at deep end 7.5 feet as the long pole / brush combination only seems to get the shiny layer off and otherwise cant hold me breath long enough to swim down and scrub by hand, any ideas appreciated. thanks
    Blue haven kidney style 16,000 gal gunnite including Spa, test Kit TF - 100
    Built 2000 deep end 7.5 feet, 2 steps at shallow end
    Original SWG then convert to chlorine
    Pentair Clean & Clear cartridge filter (4)
    Blue Haven Teledyne Laars Platinum II heater

  2. Back To Top    #2
    VinDeeLoo's Avatar
    Join Date
    Jun 2016

    Re: Black algae spots stubborn to remove

    Your FC is too low for your CYA. Your minimum FC level is 5 and your Target FC is 7.

    Use this chart - Pool School - Chlorine / CYA Chart

    I would do a OCLT - Pool School - Perform the Overnight FC Loss Test (OCLT)

    If you do not pass you will need to SLAM you pool. - Pool School - SLAM - Shock Level And Maintain
    7600 gallons ~ AG ~ Summer Waves Cartridge C Filter ~ using pump that came with our Summer Waves 18 x 48 pool ~ Taylor K-2006 (SpeedStir & Sample Sizer) ~ no well water or water restrictions

  3. Back To Top    #3
    Mod Squad
    Join Date
    Aug 2012
    DFW, TX

    Re: Black algae spots stubborn to remove

    Are you maintaining elevated FC? Something like halfway between target and shock? FC/CYA Chart That might help. Do you have an algae stainless steel brush? What about tying some kind of weights on it? Or bricks? I can't remember if there are any handy tips in this article, Pool School - Black Algae.
    TFP Moderator
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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