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Thread: Need help - mustard algae ???

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    Join Date
    Jun 2014
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    Callands, VA
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    Need help - mustard algae ???

    Please see attached photos. I think we have mustard algae, but not sure. We opened this year to clear water. Our CYA has been 60-70 all summer and FC has been between 4 and 7. All other test numbers are in acceptable ranges. Every now and then we get this line of some form of algae. Brush, vacuum, and it's back the next day. Always in the same places - on the ledge where shallow end starts to descend to the deep end, and a little bit in the deep end. It also likes the seams in our vinyl liner. If we run the FC up above 10 it goes away for a week or so, only to return again once FC is back to 4-6 range. Wife is reluctant to run FC up to recommended mustard algae shock level for fear of damaging the liner.

    1) Do you think this is really mustard algae?
    2) Is vinyl liner damage a valid concern if we stay within the recommended mustard algae shock level?

    Thank you!
    Attached Images Attached Images
    26,000 gal, IG, Vinyl, Sand, Hayward 1 HP Superpump, Hayward Goldline Aqua Plus SWG, Completed 7/2013

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    Texas Splash's Avatar
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    Re: Need help - mustard algae ???

    Good morning. I personally don't think it's MA. Mustard algae is a yellow green color and grows on the walls and floor mostly on the shady side of the pool. Pollen and dirt tends to accumulate in drifts on the floor in places with slower circulation and can often look fairly similar to mustard algae. This is in the sun and just appears to be more like regular algae or perhaps a settling of pollen. Also, with a CYA of 60-70 (let's say 70), your FC level ranges have gone too low. But the minute you suspect any algae at all, you first need to SLAM via the Pool School - SLAM - Shock Level And Maintain. Also, check your water circulation to ensure that same trouble shot is receiving adequate movement. That could be a source of your troubles. I suspect you will need to SLAM, but you could also do an Pool School - Perform the Overnight FC Loss Test (OCLT) to confirm the loss of free chlorine.

    - - - Updated - - -

    Probably would be best to post a full set of numbers as well (FC, CC, CYA, PH, TA ... CH is N/A for now). Thanks!
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
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    duraleigh's Avatar
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    Re: Need help - mustard algae ???

    That is not mustard algae. Mustard algae is a yellowish film on your pool walls and floor and does not pile up. Your pic is not mustard algae. That is algae that is dead/dying and has settled to the pool floor.

    Most always that indicates inadequate chlorine and the need to SLAM.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Need help - mustard algae ???

    ok. I'll get started on the SLAM right away. Thanks!
    26,000 gal, IG, Vinyl, Sand, Hayward 1 HP Superpump, Hayward Goldline Aqua Plus SWG, Completed 7/2013

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    Re: Need help - mustard algae ???

    I don't understand. Our numbers seem to be ok? (see below), but this problem persists. The lines form (see pics above) approximately every other day. When we brush the pool floor and walls, there is a greenish cloud that is stirred up from these surfaces. Otherwise water is clear. Chlorine numbers have been climbing with SWCG set at 30% for 12 hrs/day. Is this just dead algae that needs to be vacuumed or is there still a problem that needs to be addressed?

    8/26/15 8/30/15 9/1/15
    FC 4.6 5.0 5.6
    CC 0.0 0.0 0.0
    pH 7.8 7.6 7.8
    TA 80 80 70
    CYA 50-55 50-55 50-55
    26,000 gal, IG, Vinyl, Sand, Hayward 1 HP Superpump, Hayward Goldline Aqua Plus SWG, Completed 7/2013

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    Texas Splash's Avatar
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    Re: Need help - mustard algae ???

    Your numbers as posted are ok. The CYA is low for your SWG pool which I suspect is driving your SWG to work overtime to keep-up FC production. Regardless, if you see green clouds when you brush, that's algae, and that requires a "SLAM" (Link below). Dead algae would be more of a white/gray color. Also, you can have algae even with no CCs. We could speculate about the FC level perhaps dropping previously, but once algae is in the water, it needs to be SLAMmed to kill it. I would reference the SLAM link below, follow each step carefully, and you should be fine.

    If you have any doubt about starting a SLAM, at least run an OCLT tonight. When performing the OLCT, remember that it must be done when the sun has dropped – no sunlight on the pool. About 8 hours total is recommended. Also, your FC level should be elevated more than normal. Starting (bedtime) FC could be close to your SLAM level, but no lower than 10. Anything less and you may not receive an accurate portrayal of FC loss (by percentage), even if it’s only 1 ppm.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
    If you enjoyed your TFP experience, please consider donating to Support TFP!

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