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Thread: DE Resting on Bottom Surface or Algae?

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    DE Resting on Bottom Surface or Algae?

    I did a complete cleaning of my Hayward DE filter just last week and had an issue with the seal on the relief valve which led to some DE slurry getting back into the pool. I came back from work 5 days later, tested the water (FC 0.5, CC 0, pH 7.4, TA 110, cYA 60, CH 230) and came across this...



    The pool cover had blown off the pool and was only covering the right half of the photo as you can see. This stuff is resting on the surface of the pool and has a green/brown color to it while grey where it wasn't exposed to the sunlight. Could someone possibly confirm this is likely just DE that I can vacuum up and not algae? I'm a bit paranoid and wondering if I need to SLAM the pool now.
    28,000gal IG plaster, Leslie's Crystal Clear II DE Fliter, Pentair 2HP 2 speed, Taylor K-2006

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    Patrick_B's Avatar
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    Re: DE Resting on Bottom Surface or Algae?

    The dark stuff isn't DE, but looks like Algae, and your FC is low enough for it to grow for sure. Your Cya is a bit high,Mobutu very high with 0.5 FC. Is any of this dark stuff elsewhere in the pool?
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    Re: DE Resting on Bottom Surface or Algae?

    It's dark just in the area that got sunlight. Everywhere else it looks like grey DE sand dunes. It kicks up when when disturbed too. Doesn't algae tend to grab on to the surface and need brushing?

    CyA was brought up (for the sunlight) right after the filter cleaning per a recommendation from the Testing and Balancing Your Water sub. I brought FC up to 7 right before I left for the 6 days I was on the road.
    28,000gal IG plaster, Leslie's Crystal Clear II DE Fliter, Pentair 2HP 2 speed, Taylor K-2006

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    Mod Squad jblizzle's Avatar
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    Re: DE Resting on Bottom Surface or Algae?

    What you are describing as DE sounds more like dead algae to me.

    Based on your test results, FC dropped too low while you were gone.

    And now you need to follow the ShockLevelAndMAINTAIN Process.
    Jason, TFP Moderator
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    Mod Squad pooldv's Avatar
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    Re: DE Resting on Bottom Surface or Algae?

    FC of 7 is the target that should be maintained daily. FC should always be at or above target. Anytime FC drops below minimum algae will start to grow and the pool is unsanitary. Next time you will be away from the pool for a while raise FC to shock level.
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    Re: DE Resting on Bottom Surface or Algae?

    Thanks for all the responses. I did vacuum everything up and raise the FC back up to 7.

    Unfortunately, I have to leave again for several days and can't SLAM the pool until I get back. What would be a good level to leave the FC at before I leave?
    28,000gal IG plaster, Leslie's Crystal Clear II DE Fliter, Pentair 2HP 2 speed, Taylor K-2006

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    Mod Squad jblizzle's Avatar
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    Re: DE Resting on Bottom Surface or Algae?

    Raise the FC up to shock level. Cover the pool.

    Then follow the SLAM process when you get back.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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    Re: DE Resting on Bottom Surface or Algae?

    Got it jblizzle. Thanks!
    28,000gal IG plaster, Leslie's Crystal Clear II DE Fliter, Pentair 2HP 2 speed, Taylor K-2006

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