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Thread: how do I know if its mustard algae?

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    how do I know if its mustard algae?

    We have had to shock the pool once before and all went well. It took longer than I thought it would for the white cloudy water to clear, but we just kept filtering and eventually we had our sparkling pool back.

    This last time, it seemed like everything was OK and there was no overnight drop and no color in the pool, so we just kept filtering and backwashing to clear the cloudy water, but it never got quite right. The only strange thing was that even on the first day that we had the pool at shock level, CC was only .5. The last time we shocked, CC was up for a while until no drop in overnight FC.

    Anyway, a week later, we are back at it again. Last night I brought the shock level up higher than I thought it should be to 20 ppm instead of 16. And this morning, the CC was 1. This made me wonder if I should keep it up higher since last time at 16 ppm CC was never any higher than .5 during the entire shock process. I know that for mustard algae it is supposed to be higher?

    What is mustard algae, and how would I know if I had it?? Should I keep my shock level higher than my normal 16?

    Also - there seems to be rusty/orange colored stuff on the edges of the steps, etc. The same as last week before and during shocking.

    CYA=40, TA= 90, FC=17.5 (this morning), pH=7.5 (last night before adding tons of bleach)

    Thanks so much!

    PS - would a picture help??
    18-20,000 gal?, sand filter, IG vinyl, 1 HP 2-speed pump

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    Mod Squad Bama Rambler's Avatar
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    Re: how do I know if its mustard algae?

    A picture may help.

    If it's growing mostly on the shaded side it's probably mustard algae. If you think it is, follow the mustard algae shock treatment outlined here and you should get rid of it for good. Remember that anything that's been in the pool or is going in the pool needs to be exposed to the MA shock.
    Dave J. TFP Moderator
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    Re: how do I know if its mustard algae?

    Are you using a pool cover? Keeping a pool cover on all of the time can raise CC levels.

    Another possibility would be if you lost CYA over the winter. Losing CYA over the winter can sometimes create persistent CC levels that are harder than usual to get rid of.
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    Re: how do I know if its mustard algae?

    Quote Originally Posted by Bama Rambler
    A picture may help.

    I can't seem to get a good one....but my son, the pool brusher, said that this spot kept coming back at the beginning of the first shock, even after he brushed it again and again, and now it is in the same place after a few days of being back down to normal FC levels.

    If it's growing mostly on the shaded side it's probably mustard algae.
    It's not growing on the sides that we can see, but it seems to be in the water, and in the shadier spots of the pool, like the steps.
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    Mod Squad Bama Rambler's Avatar
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    Re: how do I know if its mustard algae?

    When you brush it does it create a cloud of dust?
    Can you pinch a sample and see what it feels like?
    Dave J. TFP Moderator
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    Re: how do I know if its mustard algae?

    yes, when we brush it creates a cloud of dust. I'll have to wait until my swimmers get home from school to ask them for a pinch...
    18-20,000 gal?, sand filter, IG vinyl, 1 HP 2-speed pump

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    Mod Squad Bama Rambler's Avatar
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    Re: how do I know if its mustard algae?

    It's likely mustard algae, so I'd go ahead and follow the shock procedure outlined for it.
    Dave J. TFP Moderator
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    Re: how do I know if its mustard algae?

    Quote Originally Posted by Bama Rambler
    It's likely mustard algae, so I'd go ahead and follow the shock procedure outlined for it.
    OK. I guess I am a little confused about how to follow the shock process for mustard algae. Last night there was no overnight loss of chlorine, but the water is still cloudy and yellowish/greenish. Do I keep the pool at regular shock level until that goes away? Will it go away? Yesterday we brushed the pool twice, but one of the spots on the steps is back again this morning even thought it was at shock level all night. Is it time to increase the regular shock level to mustard level for 24 hours?

    Thanks!
    18-20,000 gal?, sand filter, IG vinyl, 1 HP 2-speed pump

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    Mod Squad Bama Rambler's Avatar
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    Re: how do I know if its mustard algae?

    Now I'm rethinking my suggestion. Is it showing up on the tops of the steps or on the sides of the steps too?
    Dave J. TFP Moderator
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    Re: how do I know if its mustard algae?

    It's on the top and edges of the steps, but not on the sides. could it be something else?
    18-20,000 gal?, sand filter, IG vinyl, 1 HP 2-speed pump

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    Mod Squad Bama Rambler's Avatar
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    Re: how do I know if its mustard algae?

    It sure sounds like it. It sounds like pollen. Did you ever get a pinch of it?
    Dave J. TFP Moderator
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    Re: how do I know if its mustard algae?

    no, there wasn't a "pile" to pinch until this morning. is the mustard algae squishy vs crumbly, or something?
    boy, that would be great if it's not that. I don't know that pollen is an issue in our area, but maybe something else, like rust particles from when my husband was cleaning out and repainting the rusty trough around the edge of the pool? So if that is the case, should we keep normal shocking and mabye try to vacuum the what-ever-it-is? It seems like it should get clean and clear with regular shocking and filtering if it is regular algae that is making our pool cloudy and yellowy/greenish?

    I really appreciate your help trouble-shooting!
    18-20,000 gal?, sand filter, IG vinyl, 1 HP 2-speed pump

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    Mod Squad Bama Rambler's Avatar
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    Re: how do I know if its mustard algae?

    If he was grinding (or wirebrushing) rust it could be that and with time it will finally get filtered out.

    I'd hold shock level until you've passed the OCLT and then you can do a mustard algae shock or let it return to normal and see what happens.

    How long per day are you running the pump/filter?
    Dave J. TFP Moderator
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