Question about mustard algae

Aug 14, 2014
15
Dyer, IN
Hi,
I am new to the forum. I have been studying all of the knowledge and have read many of the mustard algae information and threads. I have been dealing with what I believe is mustard algae. No matter what I do, I cannot get rid of this tan substance that keeps appearing at the bottom of the pool. This is day four of Slamming at 30ppm. I have been brushing every day. Took ladder off and thoroughly cleaned it with bleach today - just brushed it before. I was still losing chlorine over night - it drops from 30 to 15 by morning. Despite having the level maintained at 30 most of the day, I still see the dust at the bottom. If that is algae, shouldn't it bleach out at some point? You can brush it and it reappears usually in a liner wrinkle within about 20 minutes. I am starting to wonder if it is pollen/dirt/sand/sawdust. But then there is that overnight chlorine loss. Four days seems very long for a level of 30 and I am making no progress. Pool looks beautiful - aside from that dust. Water is sparkling. Any advice would be appreciated.

above ground pool
17000 gallons

TH 500
TC 30
FC 30
CYA 50
PH 6.8 (after adding acid today)
TA 120
CYA 50
Phos 300
 
:wave: Welcome to TFP!!!

What does the Overnight Chlorine Loss Test say?

Also, that is not the correct process for dealing with Mustard Algae, if that is indeed your problem.

Finally, the pH test reads artificially high when the FC>10ppm ... your pH is likely WAY too low now.


I have been doing the OCLT every night. I raise it to 30, and it goes down to 15 by morning. 8 p.m. to 6 a.m. I bump it back up to 30 at 6 a.m., it holds for most of the day. In the evening I have to add about 1 gallon to bring it from 24 to 30. Next morning 15 again.

I visited the pool store today after being ready to give up. they tested the water and suggested I dump 1/2 gallon of muriatic acid in. So I did. I did not put in the phos free they recommended since it says high chlorine levels impede its ability to function.

Should I just keep going with the 30ppm? The "sand" continues to be there even in 30 ppm all day long. Also, now do I need to increase ph or will the shocking bring it up.
 
It makes no sense to lose more FC at night than during the day ... frankly that should not be possible.

There is no reason to worry about phosphates ... so do not waste money on that.

And adding acid at this point is a VERY bad idea. Please stop listening to the pool store. As I already said your pH is too low already.
 
It makes no sense to lose more FC at night than during the day ... frankly that should not be possible.

There is no reason to worry about phosphates ... so do not waste money on that.

And adding acid at this point is a VERY bad idea. Please stop listening to the pool store. As I already said your pH is too low already.

How do you get an accurate read of ph when your fc level is 30ppm or higher?
 
You can't really. You can try to dilute with distilled water, but would have to do 3 to 1 and may not be accurate.

That is why we say to adjust the pH before you SLAM.
 
You can't really. You can try to dilute with distilled water, but would have to do 3 to 1 and may not be accurate.

That is why we say to adjust the pH before you SLAM.

Ok. It was adjusted 5 days ago when I started. Probably no point in trying to increase it when I have no idea if it is high or low. Todays update, accidentally added too much chlorine last night - to 40 (i had a typo in pool calc). Today it was 24 ppm and tan dust still present. Brought it to 36 in order to keep it over 30 at all times.

Given this amount of chlorine loss, would you conclude that this has to be algae as opposed to pollen, etc.?
 
If there's that much overnight chlorine loss then there seems to be something organic that's getting broken down. With a CYA of 50 I would SLAM at 20 ppm FC. Once you pass OCLT, water is clear and CC 0.5 or less then you can raise FC to 30 ppm for 24 hours to ensure that any mustard algae is eliminated. Good luck!
 
If there's that much overnight chlorine loss then there seems to be something organic that's getting broken down. With a CYA of 50 I would SLAM at 20 ppm FC. Once you pass OCLT, water is clear and CC 0.5 or less then you can raise FC to 30 ppm for 24 hours to ensure that any mustard algae is eliminated. Good luck!

Thanks! I will keep going with the chlorine and the brushing.
 

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Thanks! I will keep going with the chlorine and the brushing.

While I had the solar cover rolled up and floating around in the pool today, I noticed a pink film on one section of it that had been basking in the sun today. Could this be pink algae? If so, what would be the best method of trying to clean the cover? This cover has been on the pool every night for the five nights of constant shocking - perhaps contributing to the overnight chlorine loss. Sigh.
 
While I had the solar cover rolled up and floating around in the pool today, I noticed a pink film on one section of it that had been basking in the sun today. Could this be pink algae? If so, what would be the best method of trying to clean the cover? This cover has been on the pool every night for the five nights of constant shocking - perhaps contributing to the overnight chlorine loss. Sigh.


Scrubbed cover with bleach. Kept shock at 30 all day. Brushed everything several times. Fingers crossed that tomorrow will be clear.
 
That is not how you fight mustard algae, review article in Pool School.

I would love it if you would elaborate. I have been keeping it between 24 and 36 ppm since 6 am today My cya tested at 40. It seems like I will need to dose it high at night to make sure it does not fall below 24. Last night it dropped from 30 to 18. I am still struggling. I added soda ash to reverse the half gallon of muriatic acid that the PS recommended. Brushing several times a day. Ladder is out and has been sterilized. Solar cover staying in to continue decontamination. But even today - from 8 am to 6 pm it lost 12 ppm - caught it just in time before it went under 24.

I really respect all of your advice and I try to be consistent in following it. Maybe it is an improvement to go from a 16 overnight loss to a 12, but holy cow it feels like this could go on forever.
 
I just meant you should follow the normal SLAM process until you pass the 3 criteria and then you raise to mustard level.

OK, so given my cya of 40, I should only shock and maintain to 16. Going up to 30 or 40 is overkill UNTIL the algae is gone and OCLT is less than 1. I will let it drift down. Only lost 10 overnight. This seems to be heading in the right direction.
 
OK, so given my cya of 40, I should only shock and maintain to 16. Going up to 30 or 40 is overkill UNTIL the algae is gone and OCLT is less than 1. I will let it drift down. Only lost 10 overnight. This seems to be heading in the right direction.

Well it has been eight days of shocking and brushing. Any idea how long it takes to eliminate mustard algae. Same tan dust at bottom of pool. OCLT was 4 last night. I am wondering if I need to change the filter sand. Any thoughts Jason?
 
I just meant you should follow the normal SLAM process until you pass the 3 criteria and then you raise to mustard level.



Zero OCLT last night. But today I lost 4 ppm during the day. I think i will add another gallon to get through the night just in case. The tan debris still accumulating in little piles and in crevices on the floor. No change in the amount of that stuff.

This is seven days of supershock SLAM plus two full days of regular SLAM - 9 total. Is there anyone who has actually won this battle? If so, what was the length of time for those folks? I am very discouraged. Considering bromine. What does dead mustard algae look like? I could really benefit from hearing a success story if one exists. :(
 

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