Can't get rid of Mustard Algae

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K

kywingnut

0
Apr 25, 2014
10
usa
Hello all. First post here. I found this site and have been reading so much information for over a week now. Very informative. Thank you!
My problem is, I have been fighting a mustard algae problem for 2 years now. I have barely been keeping it at bay, After reading the
information here, I realized using granular chlorine had raising my cya reading to almost 90. So my free chlorine level were too low.
After returning for a 2 week vacation, I found I also had a green algae problem.
First thing I did was lowered my cya reading down to 68, with a partial drain and refill.
My pool readings when I started the slam were,,,
cya = 68
ph = 7.5
total alk = 80
combined chlorine = 0

I have maintained a free chlorine level of 28 for 3 days now for this slam. Water looks clear. Green algae seems to be gone. But the mustard algae returns in very small amounts daily on the exact same spots as the day before, the same spots as even last year. (Quarter size spots)

I'm not sure if my very old liner will hold up to these high chlorine levels to much longer.

Does it sound like i an doing things correctly up to this point.

Thanks in advance, Mike
 
Are you using a TF100 or a K2006 test kit?

3 days is on the short side for a SLAM. Are you brushing your pool daily? If not, you need to be.
 
If I am treating my pool for mustard algae, I am confused at which shock level I should be at. I have been slamming my pool for 6 days now maintaining a FC level of 27/28.
Once I passed the 3 tests I was going to raise my shock level to 40 for the final 24 hours. (mustard shock level)
Is my current shock level of 28 enough to finish off this Algae or do I need to raise it to the 40 now, even before I pass the overnight test?
I still get very small amounts of the mustard algae re-occurring daily.
 
First you perform the standard SLAM at the appropriate SLAM/Shock level and ensure you pass all 3 SLAM criteria. Then for the MA portion, you use the MA FC level noted at the bottom of the Poolmath calculator for a 24 hour period. That should do it. After those processes you should not be seeing any more algae.

- - - Updated - - -

So I'm showing SLAM FC of 28, and 24-hr MA treatment FC of 39.
 
Ok, thanks. That's what I will do. I've been maintaining FC of 28 now. My water looks great, it's very clear. I haven't done a CC test or OCLT test since I still get a small amount of the mustard algae returning daily on the bottom of the pool. (several small dime sized spots)
I'm was beginning to wonder if I should just raise it up to 39 or 40 now to try to finally eliminate it. This is my 7th day of maintaining 28 FC level.
 
You sound like you are doing well. I would continue as discussed and fully complete the regular SLAM by confirming that you passed both the OLCT and CC, then if needed for MA go to FC 39 for 24 hours. After that you should be good. At the same time, do all the normal things like pump on 24/7. sweeping, filter cleaning, etc. Also make sure you have good water circulation to any stubborn areas. Good luck!
 
Hello again. I just completed my OLCT test and it was good. No overnight FC loss. CC was 0 and my water is clear. I feel like i'm all set but I still have these very small spots that appear in the same spot daily. Several of them, very small that if I don't brush them, they usually get larger. They are brownish and will puff up and disintegrate when brushed. Could this possibly still be mustard algae? I've posted some pictures but i'm sure it will be hard to tell. I wouldn't think tree pollen would come back to the exact same spots. Thanks again for your help.20150806_085517.jpg20150806_085520.jpg20150806_085549.jpg
 
Circulation patterns can cause sediment to gather in the same spots. Bump it up to MA level if you met all 3 SLAM criteria. Be sure and maintain the MA level. What you have could just be a little bit of dead algae. My dead algae was a brown color. I had to put DE in my sand filter to catch everything.
 

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My slam is complete as of Friday. I have passed all 3 test's. I've been monitoring the FC level since the kids want to swim again, it tested this morning at 19.
According to my CYA reading of mid 60's last week, I thought that was a safe FC level. I just checked the CYA level again just to be sure and now it's at 30! Took water sample to pool store to confirm and they got 30 also. I'm sure it was mid 60's last week as I had tested it several times. We have had no rain, 1 backwash and no water transfers , I don't understand how the CYA level could have dropped, pool store doesn't understand either. They tested it when it was high also. (when it was originally 100, I did a partial water transfer to get it to 65. That was over 2 weeks ago)
Any ideas why it would drop like that?
Thanks
 
We have to mark this year on the calendar for weird CYA drops. I've seen many such posts. In fact, it's happened to me twice this year with no rain or water exchange! Some of us thought perhaps there was a bad lot/batch of stabilizer at one retailer, but I bought two different types of stabilizer from two different locations over the past 3 months, and mine just dropped another 10ppm. :brickwall:. I feel your pain. All we can do is watch it I suppose.
 
Normally you shouldn't need to test the CYA very often -- monthly would be the most. The exception would be if the FC got to zero at any point in time, especially if this was followed by a high chlorine demand or significant CC, and after doing an extensive SLAM especially a yellow/mustard algae SLAM.

At least from a SLAM the lowering of CYA is not unexpected since as noted in Degradation of Cyanuric Acid (CYA), chlorine slowly oxidizes CYA. In pools at normal FC/CYA levels this is usually slow. In my pool it seems to be at around 2-3 ppm CYA per month but I have an opaque pool cover on the pool most of the time. For uncovered pools exposed to lots of sunlight, the loss rate may be greater from the hydroxyl radicals produced when chlorine breaks down so maybe gets closer to 5 ppm CYA per month (a few people report higher up to 10, but most don't without other explanations of water dilution).

A regular SLAM has 10 times the active chlorine level compared to regular FC/CYA levels while a yellow/mustard algae SLAM has 23 times the active chlorine level. So just based on this alone and using a conservative 2 ppm CYA per month base loss, a regular SLAM would lose about 5 ppm CYA per week while a yellow/mustard algae SLAM would lose 11 ppm CYA per week. If actual base loss rates were higher (closer to 5 ppm), then these SLAM rates would be proportionally higher so perhaps 10-15 ppm CYA per week for a regular SLAM and 20-30 ppm CYA per week for a yellow/mustard SLAM. If the pH is not sufficiently lowered before the SLAM begins, then the rise in pH from adding more hypochlorite chlorine will accelerate the CYA degradation since it goes faster at higher pH.

Maybe we should rethink not being able to reduce CYA by using chlorine at elevated levels. The higher pH is what concerns me as that can exacerbate metal staining or have calcium carbonate scale. The higher chlorine level also wears on anything organic so at yellow/mustard SLAM levels a week would be like nearly half a year of extra wear, but to get CYA lowered perhaps it might be worth it. Those with medium blue vinyl liners that are most sensitive to fading from chlorine would probably want to avoid such a high and long SLAM. The main thing though is that pools with high CYA levels (100+) would need extraordinarily high FC levels to get to the needed SLAM levels to make the degradation go fast enough.
 
Thanks for all of the above info. I've been monitoring my CYA and it has stayed steady at 30. Since my slam I have been maintaining a daily FC level between 4-6.
If I do not vacuum every day though, this is what my liner looks like. That is a streak of green and the spots are brown color. I still have some type of algae that I cannot seem to get rid of. I'm about ready to replace my liner as I'm not sure what else to do.
I did the overnight test last night and FC was 5 last night and 4.5 this morning. CC is 0. My water is clear. Usually the overnight test is exactly the same but I tested this morning a bit later. Everything checks pretty normal, but the pool bottom says otherwise.
Any Ideas?
Thanks20150909_084721 (2)-crop-cropyy.jpg
 
That sure does show green. With all that you have done it should not be there. Have you backwashed your filter? I wonder if something is hiding in there. Did you end up taking your steps out? How did they look?

Kim
 
Along with what Kim suggested, I wonder if it's not more of a circulation problem? For you to pass the OLCT and have such good clear water, it makes me wonder. Does that debris settle in the same location each time? That pattern would seem to indicate so. Do you happen to have any dust or pollen that typically settles around your pool each day?
 

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