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Thread: Options for mustard algae with high CYA

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    Options for mustard algae with high CYA

    I appreciate the advice available from lurking, but now I have a couple of direct questions.

    First, I am a relatively new pool owner, we bought the house and pool last year, and have had relatively good fortune so far with maintenance. Now we have a recurring algae problem that is more of a nuisance than anything- I have to brush the sides of the pool on the shady end at least every other day or the algae will take over the whole pool.

    Here are the details...

    12,000 gallon fiberglass pool with a cartridge filter
    FC is at 0
    pH is unusually high today, at 7.7 but we did get a couple of inches of rain this weekend.
    TA is at 80
    CYA is at 90

    When we bought the pool, I was told not to let the water level get below the skimmer or it would damage the fiberglass body due to the missing weight. Consequently, I don't know for certain how to drain water from the main drain at the bottom of the pool, as it's never come up. There is one valve on the pool end of the pump that I haven't messed with, so I suspect that's the one.

    Anyway, upon review of the Shock Process page, the Mustard Algae page and the pool calculator, all of the advice tells me I need to either replace a significant portion of the water in the pool to reduce the CYA value, or add ridiculous amounts of bleach in order to hit the Mustard Algae shock level.

    Are there any other options? Should I just keep brushing until the temp drops to close levels?

    Any advice is appreciated!

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    Mod Squad JohnT's Avatar
    Join Date
    Apr 2007
    SW Indiana

    Re: Options for mustard algae with high CYA

    Your problem is the 0 for your FC. It should never get to zero, even for an hour. Keep it at the target level for your CYA, and never let it drop below the minimum. Since you have some algae, it would be best to raise your chlorine to shock level and hold it there for a few days. Test it hourly at first until you know how rapidly the chlorine is being consumed.

    The drain at the bottom isn't for emptying the pool. It is a water intake for the pump, just like the skimmer.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

  3. Back To Top    #3

    Re: Options for mustard algae with high CYA

    Ok thanks. I'll keep adding bleach and scrubbing this week and make the effort to shock-n-test it hourly this weekend.

    I appreciate the guidance.

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