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Thread: MUSTARD ALGAE...Duration of Shock

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    MUSTARD ALGAE...Duration of Shock

    Hello Everybody,

    thanks to this site, I have had crystal clear water no issues at all with my pool using BBB....... until recently. I went out of town for 3 days and did not get the FC level up high enough for the time that I would be gone + alot of rain showers and I now have Mustard Algae (I read posts for hours and I am sure this is what I have). My water is still clear-blue but the algae grows on the bottom and on the sides, likes the shade and comes back to the same places after I brush/vaccum and it is yellow/brown in color. I shocked at 15ppm for 2 days, everything seemed to be clear and numbers were holding, but it returned (another indicator that it is mustard algae b/c the shock level wasn't high enough) I have a 16 X 4 vinyl intex frame pool, approx. 5100 gallons, 1000 gallon per hour pump running 24/7. Using my TF-100 kit, my numbers now are....

    FC - 4
    CC - 0
    CYA - 40
    Calcium - 100
    PH - 7.5
    TA - 100

    From poolcalculator.com says get FC and hold it @ 22ppm, so I'll put it at 24 and brush the sides/bottom @ night and at lunch if I can get home. My question is how long should I expect to have to keep the FC level @ 24ppm in a pool of this size to get rid of the mustard algae? My girlfriend has the week off and wants to swim....so you can understand my dilema Just wanted a basic timeline of when we should be able to swim again, and any other suggestions are welcomed.

    Thanks - Paul

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    frustratedpoolmom's Avatar
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    May 2007
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    SWSuburban Chicago, IL
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    Re: MUSTARD ALGAE...Duration of Shock

    You want to shock till it's dead, and the best way to tell if it's dead is to do the ole' "overnight" comparison. So shock after sunset, wait 30 minutes or so and retest, adding more if necessary, retest...then in the morning, take another reading before the sun hits the pool and compare the results. If your FC has held, or you lose less than 1ppm, and your CC is less than .5, you are done shocking. It could be 24 hours, could be 48, who knows, it's really hard to predict.

    I have no other suggestions, sounds like you have a good plan. Sorry that your gal will be disappointed....
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    Cherie's Avatar
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    Jul 2008
    Location
    Wylie, Texas
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    Re: MUSTARD ALGAE...Duration of Shock

    Hi. I just had a couple (well, a few actually) of questions to clarify something on this process. We've been battling this all summer.

    1. After you shock in the evening, how long do you need to leave the pump running and should you brush down the pool to mix it well?

    2. How long can you maintain MA shock levels of FC before vinyl bleaching begins?

    3. After the 24-48 hours and FC holds overnight, is it safe to assume the MA is dead in the filter and pipes?

    4. And finally, is it ok to spray some algaecide on the ladder (we've been taking ours out of the pool) and soak the equipment in a pool of algaecide to make sure there is no re-infection?

    Sorry for so many questions, but before finding this site, we've had so many different instructions laid out to kill this stuff...and even tried to hire a pool guy to come do it for us. And HE said we didn't have MA, that it looked like sand to him (we have a ugly gray clay yard) and we should just add 4# shock, which we did! My DH decided to listen to the 15-yr experienced pool guy and we stopped treating for MA and next thing you know, we have lesser water boatmen feeding on the "non-existent" algae, and water boatmen, feeding on the lesser water boatmen! Our pool is sparkly clear with perfect balance, but still have "sand" and chased about 6 boatmen today! :*(

    I've been studying this site for days now and think I have my routine for my final battle (now that my DH is indeed convinced that the sand is MA), but clarification of the above would be greatly appreciated.

    Thanks,
    Cherie in Texas (whew, is it ever HOT down here now!)
    32x16 buried Doughboy, 4' shallow - 7' deep
    Pentair Dynamo 1 hp, 2-speed - Pentair 150# SD40 w/zeolite (75#)
    One skimmer/two returns/Aquabot Turbo T2

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    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    Re: MUSTARD ALGAE...Duration of Shock

    You need to keep the pump running for at least one hour, but it is a really good idea to leave the pump running 24/7 when fighting algae. Algae can sometimes use up all of the chlorine in a local area. Having the pump running keeps fresh chlorine from other parts of the pool coming over to join the fight.

    There will be some miniscule amount of liner bleaching for each day you have the pool at high shock level. You shouldn't be able to see any effect for at least a week.

    The algae will be dead in the filter and pipes fairly quickly. More of an issue are any spots with bad circulation, around the ladders, lighting niches, steps, etc.

    The best idea for ladders that have been removed from the pool is a quick rinse with bleach that has been diluted with 10 parts of water to one part bleach.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Cherie's Avatar
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    Jul 2008
    Location
    Wylie, Texas
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    Re: MUSTARD ALGAE...Duration of Shock

    Thanks Jason. I think we're ready to roll now and hopefully get rid of this stuff once and for all!

    32x16 buried Doughboy, 4' shallow - 7' deep
    Pentair Dynamo 1 hp, 2-speed - Pentair 150# SD40 w/zeolite (75#)
    One skimmer/two returns/Aquabot Turbo T2

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    Re: MUSTARD ALGAE...Duration of Shock

    The battle is over...FC held completely overnight and I have no CC's but it took approx 3 days. I am sure it is gone and look forward to swimming this weekend! Again, thanks for the help. Paul 1, algae 0.

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