newbie struggle with mustard algae

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Is it at all possible this is a residual stain that has been underneath the algae? Eg. Did you try to hold a vitamin c tablet to it for 3 min? (just in case you released any sequestered iron when you were shocking -- iron stains won't respond to chlorine, but they will respond to ascorbic acid, which is what's in vitamin c, hence the test.)

I've never had mustard algae, but is it possible it's a tannin-type stain from the algae?
 
8/24 dusk. fc is 5.5?cc?0.5?ph is 7.6, cya is 40. We added 2 gallons of 10% liquid chlorine and 1 gallon of 14.5% muratic acid . Brushed walls and floor (some yellow dusts came off. ) Turned the pump on. Tested again at 10:30pm ? fc is 17.

8/25 around 9am, FC=17 and CC<0.5. The water itself is clear, but the yellow stains on walls and floor remained. Does it mean we passed the overnight chlorine loss test and the CC criterion, but not the 3rd criterion?

8/25 around 11am, FC=11 and CC<0.5. The water itself is clear. The yellow stains on walls and floor lightened but remain (look like the "during" pictures). We tried to brush some spots, but they did not come off, no more yellow dust coming loose. We added 2.6 gallons of 10% chlorine to reach mustard algae shock level (FC=24).

8/25 around 7:30pm, FC=15, CC<1.0. We brushed all over and some yellow dust came off. We added 1.8 gallon of 10% chlorine to reach FC=24.

8/25 around 8:30pm, FC is 24.5, CC <0.5.

8/26 8am, FC is 24.5, CC<0.5. Same thing: OCLT passed, CC passed, water clear, stain remains. We brushed all over and some yellow dust came off. When does this end? :grrrr:

8/26 3pm, FC=16, CC<0.5
 
We do not have Vitamin C tablet. We tried using lemon slices, compared the result to chlorine tablet. The result is inconclusive. Both seemed to lighten the stain but neither made it disappear.

From my reading, only acid wash would get rid of the iron stain. Our plaster is quite old and might not stand acid wash. Before re-plastering, I guess we could live with the iron stain. But iron stain does not become worse over night, does it? We seem to have more stain coming back in a couple of days at normal chlorine level.

Swampwoman said:
Is it at all possible this is a residual stain that has been underneath the algae? Eg. Did you try to hold a vitamin c tablet to it for 3 min? (just in case you released any sequestered iron when you were shocking -- iron stains won't respond to chlorine, but they will respond to ascorbic acid, which is what's in vitamin c, hence the test.)

I've never had mustard algae, but is it possible it's a tannin-type stain from the algae?
Click to expand...
 
From what I have gathered reading other threads, iron stains can get worse when the Free Chlorine levels are high. There are stain treatments and sequestering agents that could help if this is iron. If you pass the OCLT you may want to look further into staining as the cause.
 
8/24 dusk. fc is 5.5?cc?0.5?ph is 7.6, cya is 40. We added 2 gallons of 10% liquid chlorine and 1 gallon of 14.5% muratic acid . Brushed walls and floor (some yellow dusts came off. ) Turned the pump on. Tested again at 10:30pm ? fc is 17.

8/25 around 9am, FC=17 and CC<0.5. The water itself is clear, but the yellow stains on walls and floor remained. Does it mean we passed the overnight chlorine loss test and the CC criterion, but not the 3rd criterion?

8/25 around 11am, FC=11 and CC<0.5. The water itself is clear. The yellow stains on walls and floor lightened but remain (look like the "during" pictures). We tried to brush some spots, but they did not come off, no more yellow dust coming loose. We added 2.6 gallons of 10% chlorine to reach mustard algae shock level (FC=24).

8/25 around 7:30pm, FC=15, CC<1.0. We brushed all over and some yellow dust came off. We added 1.8 gallon of 10% chlorine to reach FC=24.

8/25 around 8:30pm, FC is 24.5, CC <0.5.

8/26 8am, FC is 24.5, CC<0.5. Same thing: OCLT passed, CC passed, water clear, stain remains. We brushed all over and some yellow dust came off. When does this end? :grrrr:

8/26 3pm, FC=16, CC<0.5

8/26 6pm, FC=14, CC<0.5. We brushed all over, even got into the water to work on some spots. Not much difference :grrrr: . We added 2 gallon of 10% chlorine to reach FC=24.

8/27 9am, FC=21.5, CC<0.5. We brushed all over.

8/27 12 noon, FC=19.5, CC<0.5.

8/28 10am, FC=17, CC=0. We brushed all over

8/28 12 noon, FC=15, CC=0.5. We added chlorine to reach FC=19.
 
We bought Vitamine C tablets today and did the test suggested by swampwoman. The VC tablet did not change the stain. Also, the stains did not get worse with high FC, on the contrary, it got worse when FC was lower, say, below 4. And we use municiple water, not well water. I tend to rule iron out. What do I do next? I am getting really frustrated.

UnderWaterVanya said:
From what I have gathered reading other threads, iron stains can get worse when the Free Chlorine levels are high. There are stain treatments and sequestering agents that could help if this is iron. If you pass the OCLT you may want to look further into staining as the cause.
Click to expand...
 

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Here is some new information which I think might be relevant.

I have a spa that got similar yellow stains. The stains in the spa behaved the same as the ones in the pool: up till today, three days of shocking and brushing, only lightened but did not go away completely. This morning, I accidentally turned the valves in a way that it drained the spa. The spa walls were exposed for about 30 minutes. Guess what? The stains in the spa are GONE!

That got me thinking. Before the "drain and fill", the stains were scattered everywhere (see the "before" pictures"). But after the "drain and fill", the walls above the line to which I drained the water down to are clean. The remaining stains are all below that line. There are even two lines in the deeper end, maybe each corresponding to the water line in the night time and in the day time during the refilling process (see the "remaining problems" pictures). So, exposing the stains to the air seems to get rid of them.

Does this mean anything?

Thanks everyone for chiming in! Without your supports, I would've given up long ago.
 
Well, in your set of tests, you reported that you had dust coming off when you brushed at one point AFTER you'd been all clear, so maybe not. eg, you've tested for metals, the sun makes it disappear when there's no water, and it is to some extent affected by direct chlorine. This leads me to assume that it is organic, and that it is likely mustard algae residue that then depopulated.

Check this thread and see if you followed those recommendations or maybe bring it up to mustard shock for another 24 hours -- pool-school/mustard_algae

Did you, for example, clean out light niche, disinfect all the equipment?

And are you actually staying above your shock level at all times, or are you letting it drop below before bringing it back up? That could be making a difference. To me you post sounds like you're dosing it, then checking at night. If instead you went above mustard shock level and then had someone at lunch bring it back up, etc., you might see better results.

I'm sorry if I've missed something you posted elsewhere, I'm not certain I have a full picture, but by the sounds of it in the past you let the chlorine drop and the stains reemerge, which suggests they're organic...and then they get worse. So it sounds like you're still dealing with active mustard algae, which causes me to ask whether or not you followed the advice in the thread and treated every nook and cranny or not. Lots of folks go on for days or weeks shocking, only to find algae hiding behind the light niche for example.

If you've exhausted all those possibilities and given it another good 24 hours at mustard shock level, you may wish to try another shock session but possibly boost it with polyquat 60 -- not cheap and not bbb, but some people have reported success with it (except it will increase your chlorine usage). Other people use enzyme treatments, as enzymes eat algae. Can't speak to whether it is effective. Thorough, consistent high shocking is what *should* work. Sorry I can't offer more assistance.
 
Swampwoman, thank you so much for following my process and giving me many thoughtful suggestions.

I will keep shocking and be more careful not to let FC drop below 17. Last time, I ended the shock process too soon and returned to normal FC level. That's when the algae came back. This time I am determined to do it right. So I should stop only when all the stains are gone? At this rate, I am afraid it would take a very long time. Is this normal for shocking to go on for weeks? Is it normal for stains to lift so slowly? I read in the pool school that we should see visible improvement everyday. I could hardly tell the difference from day to day. But it is indeed better today compared to day 1.

I have not taken the lights out. Do I need to drain the water to do so? My husband warned me about electric shock. I did not come to the lights also partly because there are still yellow stains on the walls and floor. And my thinking was, if those couldn't go away with high chlorine and intense brushing, why bother with unscrewing the lights?

Another thought, how to estimate the cost of letting the pump on 24/7? Since exposing to the sun seems to get rid of the stains very effectively, I am wondering whether a complete drain and fill would be a good option.

Please forgive me for sounding impatient. I just want to know I am on the right track and will eventually have a clean pool. Thanks again for your continuous help! I really appreciate it!

Swampwoman said:
Well, in your set of tests, you reported that you had dust coming off when you brushed at one point AFTER you'd been all clear, so maybe not. eg, you've tested for metals, the sun makes it disappear when there's no water, and it is to some extent affected by direct chlorine. This leads me to assume that it is organic, and that it is likely mustard algae residue that then depopulated.

Check this thread and see if you followed those recommendations or maybe bring it up to mustard shock for another 24 hours -- pool-school/mustard_algae

Did you, for example, clean out light niche, disinfect all the equipment?

And are you actually staying above your shock level at all times, or are you letting it drop below before bringing it back up? That could be making a difference. To me you post sounds like you're dosing it, then checking at night. If instead you went above mustard shock level and then had someone at lunch bring it back up, etc., you might see better results.

I'm sorry if I've missed something you posted elsewhere, I'm not certain I have a full picture, but by the sounds of it in the past you let the chlorine drop and the stains reemerge, which suggests they're organic...and then they get worse. So it sounds like you're still dealing with active mustard algae, which causes me to ask whether or not you followed the advice in the thread and treated every nook and cranny or not. Lots of folks go on for days or weeks shocking, only to find algae hiding behind the light niche for example.

If you've exhausted all those possibilities and given it another good 24 hours at mustard shock level, you may wish to try another shock session but possibly boost it with polyquat 60 -- not cheap and not bbb, but some people have reported success with it (except it will increase your chlorine usage). Other people use enzyme treatments, as enzymes eat algae. Can't speak to whether it is effective. Thorough, consistent high shocking is what *should* work. Sorry I can't offer more assistance.
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