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Thread: I think I have mustard algae

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    Join Date
    Jul 2007
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    Florida
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    I think I have mustard algae

    I wasn't going to post anything about my algae problem because I thought that I beat it but I am not so sure. After testing today and readig a few posts on mustard algae, I am wondering if this is my problem.

    I test FC and PH daily and my numbers have always been fine, but about two weeks ago I started to see some greenish spots on the sides of my pool and some brownish spots on the floor. They seemed to mostly be where there was shade. Anyway, I would scrub them and check my numbers, including my CC, and it all seemed fine. A couple of days later the spots would be back. (Also the water has been clear and blue as always.) Cut to last Monday when I figured I should shock the pool. I took my FC level to shock, 16 (I shocked at algae level and not mustard algae level). I ran my filter 24/7, and scrubbed a few times a day. I ended up doing this for about 5 days until it seemed like the spots where not returning and my FC level held throughout the night. This past Saturday I cleaned the filter well and started to run it on my normal schedule, 8 hours per day. Now today, Monday, I tested and my FC was 9 but my CC was .5 again.

    As I posted earlier, I am going away for 10 days in a few days and I am concerned that I will not have this all straightened out.

    My questions are, does this sound like this could be mustard algae? What should I do next to make sure I am rid of it?

    My most recent test numbers are:
    FC 9
    CC .5
    PH 7.8
    TA 70
    CH 370
    CYA 40

    Looking for any advice.
    9K IG Gunite,1 hp. pump, Sta Rite 1-100 cartridge filter, auto chlorinator, sheer decent, built 2007.

  2. Back To Top    #2
    tagprod's Avatar
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    Re: I think I have mustard algae

    I think you need to shock it. I like to go a little higher than what you think you need to shock. If you've been shocking at 16 - I'd kick it up to 20 and hold it there. Test as often as possible and add chlorine to keep at 20. Brush, Brush Brush the pool. Most importantly test after the sun goes down and again first thing in the morning. When you can hold it overnight with 0 CC's you should be done. I would run the filter the first 24 hours straight. I've had a ,ustard algae problem and that's how I dealt with it and I got rid of it in 2 days. I caught it very early and dealt with it aggressively.
    Brian
    20K IG Gunite w/ raised 7ft spillover spa. 1.5 HP Hayward Northstar pump 425 sq ft Hayward cartridge filter, Colorlogic lights AquaRite SWG AquaLogic PS-8 control
    1hp pump for sheer descent

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    TizMe's Avatar
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    Re: I think I have mustard algae

    Is there maybe a neighbor you trust that might come over and perhaps pour at least one bottle of bleach in nightly and give the pool a brushing? I think having one bottle added nightly is better than none at all. If it were me I would leave the filter running 24/7 too. If you can get somone to come and check the pool nightly and maybe in the morning too then it is at least being tended too while your away. JMO

    Correct me if I'm wrong too, but isn't mustard algae a yellow/brown color? But as Tag says if in doubt shock ..... it wont hurt! I just went through the same thing with cloudy water and suspected and algae bloom starting so I shocked and ran the filter 24/7 and now its cleared up.
    Les
    Don't have a pool right now. Just sharing what I have learned over the years!
    Helpful Links:
    Pool School,Pool Calculator,Cl/CYA Shock Chart,TF Test Kit
    Doing BBB and loving it!

  4. Back To Top    #4

    Join Date
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    Re: I think I have mustard algae

    I was running my filter 24/7 for 6 days. Saturday I went back to my normal run, about 8 hours and let the FC slowly drift down. Now yesterday, Monday, my CC tested at .5. Is this an indication that I need to shock again?

    There are no spots on sides and the water is crystal clear.

    Also, by my previous description, does it sound like mustard algae? If so, don't I need to schock at a higher level?

    Thanks for the replies.
    9K IG Gunite,1 hp. pump, Sta Rite 1-100 cartridge filter, auto chlorinator, sheer decent, built 2007.

  5. Back To Top    #5
    JasonLion's Avatar
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    Re: I think I have mustard algae

    Don't worry about CC at 0.5. It could indicate algae or it could just as likely be nothing. If CC goes higher than that then you have a problem.

    When fighting mustard algae you do often need to have a final 24 hour period at a higher shock level to really get rid of it forever. This is not always required and if it isn't mustard algae then normal shock levels are fine. It partly depends on how throughly you brushed everywhere. Really through brushing and normal shock level will usually do it. The higher shock level at the end takes care of spots that didn't get brushed.

    Mustard algae does have a distinct yellow/brown/green tint to it. It doesn't really come across in this picture but that should help give you an idea of what mustard algae looks like.
    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

  6. Back To Top    #6

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    Re: I think I have mustard algae

    Thanks Jason, I feel more confidant the I got rid of it. I'm pretty sure that it was mustard algae that I had and I think it is gone.

    What would be a safe level to keep my FC at while I am away, with a CYA of 40? By safe I mean a level that would keep the algae from coming back. Would going on the high side be too much since I had it at shock level for a week?
    9K IG Gunite,1 hp. pump, Sta Rite 1-100 cartridge filter, auto chlorinator, sheer decent, built 2007.

  7. Back To Top    #7
    JasonLion's Avatar
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    Re: I think I have mustard algae

    I would aim to keep FC at 4 or higher. It is probably a good idea to aim quite a bit higher during your vacation, to help just in case something unusual comes along, a storm say.
    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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