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Thread: Mustard Algae Confusion

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    Mustard Algae Confusion

    So... A new pool season, yet another question about MA.

    Background: I have been managing a minor case of MA for the past 2 years. It never gets out of control, but I have yet to beat it despite attempts at MA shock, frequent brushing, etc.

    This season appears to be no different. While keeping the pool at proper FC/CYA ratio, MA will *slowly* grow. My standard protocol has been to brush when I see the first hint of yellow and that keeps it at bay for several weeks. (My guess is that if I brushed every week I would never see it.)

    Question: Shouldn't brushed off MA lower FC levels in a similar way to garden variety green algae?

    I ask because yesterday I noticed a "heavier" growth than normal after a few days of minor neglect. So after brushing the entire pool, which made the water slightly cloudy, I surmised that the FC had dropped to close to zero and added 12ppm FC to head off any growth of the brushed off algae. Today I tested the water fully expecting an FC value considerably less than 12, but instead measured 11.5!

    Obviously this means that FC was not as low as I had guessed to begin with, but I'm still confused about the role of mustard algae in regard to FC. First of all, I don't really understand why it always remains in check instead of taking over the way that green algae does. And secondly, I totally don't understand how I can never really measure the impact on FC even after brushing away what seems like a significant amount of it. Just doesn't seem to be behaving as I would expect algae to behave.

    Anyone care to venture an idea(s)?

    TIA,
    Beez
    20K gal IG plaster pool, Manually chlorinated with 6% bleach, 1.5 HP Sta-Rite Dura-Glas II pump, Pentair FNS Plus 48 DE filter, Polaris 280

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    Re: Mustard Algae Confusion

    I have struggled with mine for about a year. I have even kept the FC level significantly higher than the minimum and still get a little bit of mustard if I only brush the pool once a week. A little over a week ago I did MA shock and I haven't had any signs since then.

    I suspect mine is warm water temps, a slight weak area in terms of circulation, and not killing it all during previous MA shock attempts.

    What is your water temperature? How good is your circulation?

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    Re: Mustard Algae Confusion

    I get mustard algae in the NW corner (shady) of my pool each year.....unless I do one thing....BRUSH

    I do keep adequate chlorine in the pool but still get it in that spot. I am too intellectually lazy to try to understand all the variables. I just know that brushing twice weekly is a cure and I never think about it now that I have it under control.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Mustard Algae Confusion

    Water temp is definitely warm, but circulation is good. I hear you on the brushing Dave, and now that I have a full-blown case of the mustards there is no alternative.

    How about the effect I'm seeing with the FC? The stuff grows, so it is obviously alive; but it must not be very vigorous. Hardly dents the FC even when there is a lot of it.
    20K gal IG plaster pool, Manually chlorinated with 6% bleach, 1.5 HP Sta-Rite Dura-Glas II pump, Pentair FNS Plus 48 DE filter, Polaris 280

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    Re: Mustard Algae Confusion

    Sounds similar to what I faced when I opened. I suspected mustard last year when the same shady spot kept getting bright green/yellow algae growing. My FC demand didn't seem to be high to me and I had your same question.

    Opened to a mess this year, got it clear then BAM at seemingly normal CL levels the same culprit spots had algae growth. This year I took the lights out. Also found algae hiding around my light niches and under my steps. Brushed brushed and brushed while taking it MA slam level.

    I'm getting better at brushing more often. I think we've been clear of it for about a month now. I check those spots frequently for any sign of algae and brush them just as frequently.
    18*36*23 true "L" vinyl IG 29,000 gallons. SWG. TF-100 test kit.
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    Re: Mustard Algae Confusion

    Quote Originally Posted by Beez View Post
    Water temp is definitely warm, but circulation is good. I hear you on the brushing Dave, and now that I have a full-blown case of the mustards there is no alternative.

    How about the effect I'm seeing with the FC? The stuff grows, so it is obviously alive; but it must not be very vigorous. Hardly dents the FC even when there is a lot of it.
    I don't think I noticed a significant consumption of FC whether the MA is visible or not. I just installed a swg a week ago, so my "feel" for chlorine demand needs to be re-learned a little bit. I am currently increasing the CYA level for swg settings, and I'll be curious if any of it makes a difference in the long run. I think the best thing you can do is something like a 48 hour MA slam, brushing a lot. And then let the FC drift back down and see if it made a difference. We might have to deal with brushing twice a week. It stinks, because you follow all the scientific means for maintaining FC based on your CYA, and MA still rears its ugly head. I know mine is better in the winter when water temps are lower.

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    Re: Mustard Algae Confusion

    How about the effect I'm seeing with the FC? The stuff grows, so it is obviously alive; but it must not be very vigorous.
    My experience is the same as y'alls.....not much chlorine consumption at all.

    In August, when mine seems to be the worst, I actually brush when I don't really see it because I know EXACTLY where it will start and I think getting a little jump on it seems to help keep it at bay.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Mustard Algae Confusion

    When you keep chlorine at "normal" FC/CYA levels, it partially keeps yellow/mustard algae from growing as fast as it would if the chlorine level were zero. It's not enough to prevent it from growing since it's a heartier algae compared to green and black algae and would need roughly double the normal FC/CYA level to prevent it from growing. The chlorine level doesn't drop very fast when it's around for two reasons. First is that there isn't typically as much of it as it tends to prefer shade and second is that it's heartier so chlorine reacts more slowly with it (that's why it takes a higher active chlorine level to kill it).

    You can either try to completely eradicate it or you can have higher chlorine levels or you can live with it and brush it away or you can use alternative methods as a last resort (e.g. algicide or phosphate remover, but note that most algicides are not effective against it -- neither Polyquat nor borates are great against it).
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: Mustard Algae Confusion

    Thanks, y'all. Hopefully I will remember this so that I don't ask the same question again next season. I have a funny feeling this stuff is review material from last year...

    Happy swimming!
    20K gal IG plaster pool, Manually chlorinated with 6% bleach, 1.5 HP Sta-Rite Dura-Glas II pump, Pentair FNS Plus 48 DE filter, Polaris 280

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    Re: Mustard Algae Confusion

    Boy did I speak too soon, and too arrogantly against the yellow algae. It. Took. Over. Trying to shock it out now. Wish me luck...
    20K gal IG plaster pool, Manually chlorinated with 6% bleach, 1.5 HP Sta-Rite Dura-Glas II pump, Pentair FNS Plus 48 DE filter, Polaris 280

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