Mustard algae miseries

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CatherineFM

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Jun 27, 2007
8
I'm another one doing battle with this beast. I am in my third year with a 22' Sofpool and until now the only problem I've had is iron in my well water, which I've been able to manage with metal sequestrants. (Or chelators? I confess I'm not clear on the differences or which I've been using -- probably, I suspect, some of each.) The first year with the pool, I used some kind of expensive chlorine-substitute (Soft Swim, maybe?) from the pool store. It worked fine but cost a staggering amount of money. That winter I found Pool Forum, learned that I didn't need to mortgage my first-born to the pool store, refilled the pool with new water in the spring, started over with BBB and happily used it all summer with a sparkling clear pool.

But THIS year got off to a bad start. Explaining how it happened is too long a story to tell, but to keep it short, we ended up having to refill the pool again, and this time it took me a long time to get ahead of the iron. I deferred adding much chlorine while I worked on clearing the iron because I didn't want coffee-colored water. When I got ithe water blue, there was yellow-brown powdery stuff in the bottom of my pool. I thought it was precipitated iron (I didn't know that mustard algae exists.) So I held back on chlorine for a while longer while I tried to adjust what I still thought was a metal problem . . . until I realized, too late, that the dratted yellow-brown stuff was GROWING.

By now I am quite sure, sadly, that it is algae and not pollen. It behaves exactly like everyone who describes mustard algae says it behaves: it grows on the sides of things, it likes the shady parts of the pool, it collects in depressions in the pool bottom, it makes yellow clouds when I brush it, and worst of all, every single time I get rid of it, it comes back. I am starting on another campaign today to get rid of it, based on what I've read here. I vacuumed and brushed and shocked yesterday. Today the water is blue and clear and sparkling but sure enough, when I brush the bottom there are clouds of yellow and I know if I let those CL levels drop at all, it'll be back. I think I know what to do, based on the other posts in this section. But I do have a couple of questions.

First, I am not entirely sure of my CYA level. I have a Taylor K-2005 test kit and the scale on it for CYA stops at 30. I apparently have less than that: the black dot disappears when the water level has just reached the very top of the tube. Do you think that means my CYA level is 20? That would be about right for the amount of stabilizer I added earlier this summer. Should I add more now? Or is it just as well that it's low while I'm fighting off the dratted algae, since that means the chlorine will be more effective?

Also, I have a resin ladder that is full of nooks and crannies that I can't reach with the vacuum or the brush. I can see yellow stuff in there. I am afraid it will re-infect the pool. Would it be best to leave the ladder in place while I'm shocking, then get it out, take it apart and get it clean before putting it back in? Or should I do that first?

Has anybody out there actually vanquished this stuff once and for all? I would love to hear about it. I need a dose of hope!

I know you'll want a full set of numbers. I'll post them shortly, after I do another test -- thanks!!
 
Several people have had success fighting mustard alage!, and several have had on going problems. My best guess is that you really need to be careful to keep the FC level up to at least the max column from Ben's best guess chart after you are done shocking to keep it from coming back.

Given that the black dot did disappear I wouldn't add more CYA. Based on your description I would call your CYA reading 25-30. It is impossible to get an exact CYA reading, there is always some range that it might plausibly be in. Lower CYA will mean less chlorine to add to fight the algae, but more loss to the sun. Neither effect is large in that general range of CYA, so not much point in changing it (unless you decide to go up to the 80-90 range to reduce sunlight loses.)

I would clean the ladder before shocking, and put it back in after bringing the water up to shock level. You want any visible algae cleaned off of it and then expose it to shock levels of chlorine. You could also take it out and clean it with a dilute bleach solution and then not put it back in until you are done, but I worry you might miss spots. Also, to be through any other pool tools/toys that go into the water reguarly should be in the pool when shocking or wiped down with a dilute bleach solution.
 
Thank you!! At your estimate of 25-30 CYA, I would be looking at a much higher shock level for mustard algae than I thought. And that might explain why the chlorine reading I just got when I checked is considerably lower than I thought it would be. (It's a sunny day, too, so that's probably also part of it.) Here are the numbers I got:

FC = 9 (using the shot glass method, so that's somewhat of a guess. I wanted it to be 13.)
TC = 9 (I think. I confess I find it really, really hard to see a difference in the colors for this.)
CC = 0 (but can that be right when I KNOW there's algae in there?)
PH = 7.8 (it was 7.3 before I shocked.)
TA = 120
CH = 190
CYA = 25-30 best guesstimate.
 
Whick kind of test are you using for FC and CC?

I highly recommend the FAS-DPD test, such as the one that comes in the TF Test Kit or the Taylor K-2006. It will measure FC and CC up to 50. You can also get the FAS-DPD test without the rest of the kit from Tayor, though I forget the part number.
 
For yellow/mustard algae, you need to shock with 60% of your CYA level so 15-18 ppm FC, in your case with 25-30 ppm CYA. Lower your pool's pH to 7.2 before shocking and then maintain the shock level for at least 2 days (3 is better). Yes, put the ladder and anything else that will going back into the pool which includes poles, brushes, etc. Wash your swimsuits with hot soapy water (yes, they may fade slightly, but it's ensure you won't reintroduce the algae). If you use a pool cover, have it on the pool during one day and night during this process.

To ensure keeping away this algae, you will need to maintain a minimum FC level of 15% of the CYA level (about the "Max" column in Ben's Best Guess Chart).

Richard
 
Thanks, everyone. Jason, I don't have the FAS-DPD test. Wish I did. I have the taylor K-2005, which has the test that stops at 5. I will look into buying the stand-alone FAS DPD from Taylor because I really don't trust my color matching abilities.

Thanks so much for the numbers, Chem Geek. Today I failed utterly in maintaining the necessary level -- I work half an hour away so I couldn't do any testing during the day. Things were fine when I left at 8:30, but I came home after a day of sunshine to find that the FC was 7 and sure enough there were a few teeny tiny little spots of returning dratted stuff here and there. I dumped in enough bleach to get it to your levels and will check it and do so again first thing in the a.m. Unfortunately I have to go to work again tomorrow. . . then I'll be here on the Fourth, but then we are going away on Thursday for four days!! I may have to settle for a kind of holding pattern until after we get back, and then repeat the two or three days of shocking if necessary. (I can ask the guy who will be caring for our cows while we're gone to keep adding bleach every day, but I can't ask him to do all the rest of the testing and brushing that's really required.) Argh.

thanks so much, again, for the advice and support.
 
Oh, and I meant to add, before, to Richard / Chem Geek: great suggestion about the pool cover. I don't have one but this might be a really good time to get one. i assume the theory is that it slows down the burning off of the chlorine?
 
Yes, if the cover is opaque to UV, then you save a lot of chlorine. Unfortunately, the solar covers that are good at lighting light through to help heat the pool aren't good about keeping out UV. The more opaque covers keep out UV and still keep the heat in the pool so for saving on chlorine they are the best, but may not heat the pool as much (not sure about that). Mostly the covers keep the heat in at night. Mine is opaque but pretty thin (since it's an automatic safety cover) so doesn't keep heat in at night as well as a solar cover, but it does keep UV out completely.
 
Thanks so much for the cover info. When we first bought our pool I was sure we would need at least a cover and perhaps a heater because we live in an extremely cold part of Upstate New York. (In the 20 years we've lived here, we've had frost in every month of the year except July.) But I have been very surprised at how quickly the water gets warm and then how consistently it stays there. I wonder if it has to do with the very dark-blue, almost black outsides of the Sofpool.

I'm encouraged tonight. The pool held its shock levels very well during the day, even though I wasn't here to monitor it. There is no trace of anything yellow or powdery anywhere. Now to keep it like that.
 
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