Going through shock process for Mustard--questions?

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budysr

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Aug 26, 2007
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Pensacola
After going back and forth countless times the past few weeks over whether I have mustard algae or pollen/dust that continually shows up all over the bottom of my pool as soon as a day after vacuuming, I decided to go through the shock process as if I do have mustard algae. I want to post my experience to make sure I am doing things right.
First I vacuumed the pool bottom clean yesterday morning and then added enough bleach to get to 25ppm(cya is 40). Yesterday was raining off and on all day but never a heavy downpour. Tested about an hour after adding and got a reading of 20ppm so I added enough to get back to around 25-26 and let it go till right before dark. Tested again(right before dark) and showed 20 again(maybe this bleach isnt as potent as I thought) so I added enough again to get to 25 and called it a night. This am I tested and have 21 maybe 22(doesnt look like it rained last night much at all)
The thing that baffles me is that the brown spots that have plagued me have reappeared in the bottom at different parts of the pool from yesterday afternoon to this a.m. Am I at a high enough level to come to the conclusion that this is dust/pollen and NOT mustard? I thought I read somewhere that mustard would not reappear while you are at a shock level? Or is this just a nasty case of mustard that isn't going away this easily? I might add that there is nothing growing on the wallls and never has been.
Should I continue to keep the pool at a level of 25ppm even in the day?(today is sunny and the rain looks to be gone)
 
If your CYA reading is right, then FC around 15+ and brushing/vacuuming will make mustard algae vanish, at least for the moment, and it won't come back as long as you keep FC high. If it is reappearing after cleaning it up at high FC levels then it isn't mustard algae.
 
Thats what I figured. Thanks Jason for confirming that for me. I guess its time to figure out another way to get these spots to keep from coming back and I can eliminate mustard algea as the culprit.
 
Hi budysr. Let me know if you figure it out because we have the same problem! Only my FC (not at shock level, but normal level) didn't change overnight -- the three nights in a row that I checked it! But the stuff just comes back and comes back and we even vac'd to waste and backwashed in July! It was clear for a day. I'm using the skimmer sock now and it catches a LOT of tannish looking stuff. But it still plagues the bottom of our pool!

I was going to do exactly what you just did, so I don't need to now! I also, at the suggestion of a moderator, collected some, put it in a clear container and sat it in the shade, taking pictures each day to see if it was growing. It didn't change any. I may do this experiment again, only this time, set it in the sun instead.

But would still like to know how to get rid of this stuff. We didn't have it the first month our pool was open.

It's very frustrating, isn't it?
 
budyser,

go back to what you already know..........only two things consume FC....sunlight and organics in your pool. You are losing FC overnight (I assume your testing methods are FAS/DPD which is the only way to do this) so that eliminates the sun.

My bet is what you are seeing on the bottom of your pool after attaining shock level is "carcasses" of the algae that you have killed. I also suspect you aren't get rid of them because you are not keeping your shock level high enough long enough. Even if you do keep the shock level up, algae, regardles of the type, will quickly reappear if you give it a small window of opportunity (low FC). Once that occurs, you will start the process all over....depositing more brown stuff on your pool floor ad infinitum.

Algae is your enemy and chlorine is your friend.
 
There have been a lot of reports this year from sand filter pool owners complaining of sandy colored looking crud "is it algae?".... :scratch:

For sand filters, you can try a slurry of DE in the filter, but you have to repeat this process every time you backwash. You can also use skimmer socks, see if that helps. I think people (I'm guilty of it too) of wanting to get every last speck off the floor for fear we'll be judged as failures if our pool isn't "show off spotless". Try Cherie's trick, if it was algae I think it would grow (in the shade too, Cherie, so I don't think it's algae). But I think with keeping your shock up that high, and then you vacumed and it returned, that it's not algae growing, its just stuff settling in that your filter doesn't get.

You may be on to something, as for the bleach strength. You said the first addition you tested shortly after and then bumped it up again, aiming for 25, but you didn't test it shortly after the second addition, you tested in the morning. So in my opinion, there remains open the possibility that you did not reach 25 and you really can't compare the morning results, because you didn't retest. Know what I mean? What kind of bleach was it, and is it possible it's lost its strength? Just covering everything here... :)

Have you tried the skimmer socks? I really feel like this is a filter issue. There have been several threads this summer like this one, and everyone reporting the problem has a sand filter....
 
fpm wrote:
Have you tried the skimmer socks? I really feel like this is a filter issue. There have been several threads this summer like this one, and everyone reporting the problem has a sand filter....
Click to expand...

Then, to what do you attribute his 13-14ppm FC loss in less than 24 hours...around 4ppm of which occured overnight?
 
The daytime chlorine loss is presumably sunlight and can be ignored. But the overnight chlorine loss means there is/was algae, or some other organic material, in the pool.

The description does sound like dead algae "raining" down on the bottom of the pool, as duraleigh suggested. That is common enough with various kinds of algae. The description doesn't really sound like mustard algae, though it can't be completely ruled out yet.

Regardless of what is actually happening, the first step is to continue shocking the pool until the FC level remains the same overnight and CC is 0.5 or lower.

It would also be a big help if you could post a full set of current water test results and tell us what FC level you were maintaining before you started shocking the pool. That might help clarify what is happening.
 
duraleigh said:
fpm wrote:
Have you tried the skimmer socks? I really feel like this is a filter issue. There have been several threads this summer like this one, and everyone reporting the problem has a sand filter....
Click to expand...

Then, to what do you attribute his 13-14ppm FC loss in less than 24 hours...around 4ppm of which occured overnight?
Click to expand...

13-14? He said he added enough bleach to reach a target of 25, but he never tested it to confirm it was reached. The OP was...

budysr said:
First I vacuumed the pool bottom clean yesterday morning and then added enough bleach to get to 25ppm(cya is 40). Yesterday was raining off and on all day but never a heavy downpour. Tested about an hour after adding and got a reading of 20ppm so I added enough to get back to around 25-26 and let it go till right before dark. Tested again(right before dark) and showed 20 again(maybe this bleach isnt as potent as I thought) so I added enough again to get to 25 and called it a night. This am I tested and have 21 maybe 22
Click to expand...

So again....he added bleach to reach a target of 25, he tested, he came up short so he added more bleach. It is possible there is algae present and the chlorine was consumed rapidly....but then he said he added more to reach the 25 mark. He did not retest to see if he reached it.

When he tested in the morning, it shows a loss of "maybe" 3 or 4, IF in fact he reached 25 at all. That was my only point, that without a test to compare it to, how do we know if there was any loss?

All I'm saying is, if you look around the forum, there have been several posts like what the OP described, and I can't help but wonder if people are assuming it's algae when in fact it isn't algae at all?
 
I went ahead and added enough to get to 25 again(not tested to confirm though) yesterday(sunday morning) before I left for the day to work. It did stay sunny and hot all day and when I got home and tested last night at dark I had 13ppm of FC. Lost quite a bit during the day. However I do not see as many brown spots reappearing(still a few small ones) and it was very windy so I have lots of leaves on the bottom. I went ahead and added enough to get back to 25 again last night and left the pump on low all night but I did not retest to confirm the reading. It rained this early this a.m. and hard for awhile but not overly excessive rain. When I tested this a.m. after the rains, I got 21ppm and don't seem to see any "new" brown spots but there are still some small spots. I didn't have time to brush or vacumm and have gone back to work for the day. I left the FC at 21 this morning but have plans to re-test and super-shock again tonight unless you guys think otherwise. This would be night 3 that I would have shocked to 25 after dark.
my cya is 40, TA is 80, CC's always test less than .5 and I had been running around 3 to 5 ppm on a daily basis although I was running less than that earlier in the summer before I confirmed the cya level. It IS possible that I had a period of time with FC levels a little lower than what they should have been although I have been pretty consistent with the upkeep.
 

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With CYA around 40, you should expect to lose a bit over half of your FC level during a sunny day. So the day time loss is not surprising at all.

One useful test is to measure the FC level in the evening, at least an hour after the last chlorine addition, and again first thing in the morning. If the FC level falls overnight then there is still something growing in the water.
 
When I got home this afternoon I tested(after sun passed) and got a FC of 14ppm. I went ahead and vacuumed(with my filter vac) all the leaves and the areas that still had some brown crud, although I have to admit that it was a lot less than has been lately. Added enough chlorine to get back to 25 maybe 26 and I plan on testing here before it gets late to see what I have tonight. Also backwashed with the idea of getting out of the sand filter whatever I just sucked into it BEFORE it gets back into the pool. It could be my imagination but my water does seem to look clearer than it has in awhile and I never really thought it wasn't clear in the first place.
Anyways...thanks you all for chimeing in with comments on my problem.
One more question for tonight.......with this being the third night that I have shocked the pool past the mustard algea level, can I call it quits on the extra bleach tomorrow if the water looks good? Keep in mind that I have kept the pool no less than normal shock levels the past 3 days but only at mustard shock levels at night.
 
Tested last night after the last dose and got 24.5ppm. This a..m. I tested and got 24ppm but I did notice that some more leaves blew in the pool overnight and sank to the bottom(could that cause a slight FC loss?). I feel pretty confident that the FC tests last night and this a.m. where close enough to be the same or certainly less than 1ppm in difference. The water does look really clear and sparkleing. I did notice just a couple of tiny brown spots but still think that it could be pollen or dust from the trees.
At this point, I still can't say for sure if I had mustard algae or not but if I did, I think I have done enough to kill it.
 
It sounds like you have met the three criteria that would make your process complete.

Incidentally, chemgeek first posted those three things and I see a lot of us adopting that as a standard that's easy to understand. Thanks, Richard!
 
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