I am so confused about mustard algae...

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pisymbol

pisymbol

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Jul 11, 2014
153
NJ
Here is the story, last night I had the following numbers when I noticed what I thought was yellow algae:

FC: 1.5ish
TA: 200
CYA: 35ish
ph: 8.0

I have 40k gallons. So I vacuumed the pool, brushed everything under the sun (well moon), and then dumped 7 pounds of dry acid in waited an hour or so, got the ph down to a nominal level, and then added 7 pounds of 73% hypocarbonate to start the SLAM process (shooting for about 18-20 FC). Pump was running all night.

Well I just woke up and the water is not only cloudy, but the floor has even MORE algae on it. Does that make any sense? Does algae grow faster at night or something? How can algae grow so quickly at these levels of FC?
 
Wildcat said:
You say high levels of CL based on what you added, I guess. What are your measured PH, TA and FC/CC levels this morning?
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Here they are:

FC = 15.21
TC = 15.21
CC = 0
ph = 8.5
CH= 205
TA = 176
CYA = 87
Copper = 0.1
Iron = 0

(courtesy of our local pool store)

I have now cleaned and scrubbed the pool again. The CYA number is odd to me (I could have sworn it was 37ish at one point - I use calcium hypocarbonate (68-73%) as my main source of chlorine).

So according to the chart I should go up to like 46ish ppm. That really is not tenable at this point. Isn't 15 ppm enough to at least prevent growth and slowish death?

As a last ditch effort I have dumped some Pink-X in it as the local pool guy CLAIMS that other customers have had a lot of success with it (could be a lie, yes, but what the heck).

Tonight I was going to dump a little more chlorine in it and then test again tomorrow morning.

One thing I still don't understand is how algae is growing at these shock levels so quickly overnight, that makes no sense to me.

Also how do you do a SLAM if you need more precision than the Taylor tests give you? (K-2006 I'm using, it's kinda hard to measure a drop of 1ppm using colors, honestly).
 
ping said:
To fix this pool the way we suggest you will need to buy a TF-100 test kit, see my signature. Pool store testing is not reliable enough and we need to know the true CYA level.

Please read the following to articles:

ABC's of Pool Water Chemistry
SLAMing Your Pool

Could it be pollen?
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No, those numbers are indeed reliable. They are using a digital reader (it's the WaterLink Spin Lab). Unless you have a viable reason to dispute this, I'd like to work off these numbers (which btw basically correlate with what I see with my Taylor K-2006 which is somewhat equivalent to the TF-100).

How do I tell if its pollen?

Also, note I've read both articles, neither of which address my current concerns.
 
Butterfly said:
I suggest you test with your Taylor kit and post your numbers for us.
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Just came back, well it's back again and it's all over the place. I am at a complete loss.

According to Taylor:

FC: 15 ppm (I had to use the 1.8->9mL dilution test)
CC: 0 ppm
PH: 7.4
CYA: 85ish when the black dot disappears

According to the SLAM page, I would have passed the test (<1ppm and CC of <0.5ppm). I may run to the pool store to just correlate my results with my Taylor.

Here are some pics of what I see.

I realize the pictures aren't great, but there is one in particular where you can see yellow stuff on the liner (vertical white line).

The reason why I am of the belief that it's yellow algae is that I don't see pollen around the pool (at least anything extreme).

More context: I inherited all of this in July (new house) and the local pool guys where taking care of it as per the last owner. When I first entered the pool, the entire floor was a bit slimy but the water was clear. They had trichlor tablets in the skimmers and by the time I tested my CYA it was over 100. This is my first pool and I was already like huh? Aren't these guys suppose to know better?

Anyway, it's the tail end of the season and I am clueless on how to determine dirt/pollen vs algae. The FC did go down to 0 at one point in the season due to negligence on my part (work was just insane). I then proceeded to essentially SLAM until I got to the point of reasonable overnight numbers and have remained at fairly stable FC counts (I've been keeping it above 5ppm for most of the season).

Here is the thing I don't understand: I never see algae on the walls of the pool. Never. Only on the floors which also includes the slopped floors to the deep end. And it's rampant in the sense that it accumulates overnight even at 15ppm. Finally, it accumulates heaviest in the same spots. I am currently vacuuming it up with my Dolphin Z5.

I'm really frustrated (you can probably tell) because no one told me taking care of a pool was going to be this difficult. I have countless of colleagues and friends who have pools, no one has ever had mustard algae before. Again, I'm at a complete loss.
 
Based on history, it sounds like you could have MA. However, can you scoop some up between your fingers? Algae feels slimy, sand/dirt feels gritty & pollen feels squishy. These are all technical terms :wink:

Have you tested the CH? Using cal-hypo exclusively will cause it to rise above recommended levels.

If you do not have the FAS/DPD test, you NEED one!
 
Butterfly said:
Based on history, it sounds like you could have MA. However, can you scoop some up between your fingers? Algae feels slimy, sand/dirt feels gritty & pollen feels squishy. These are all technical terms :wink:

Have you tested the CH? Using cal-hypo exclusively will cause it to rise above recommended levels.

If you do not have the FAS/DPD test, you NEED one!
Click to expand...


I just discovered that I have a K-2005 not a K-2006. Sigh. It's the end of the season, I can by a TFT-100 but I rather wait till next year.

I did try to pick some up, it didn't feel overtly slimy but it also didn't feel squishy. But if it was sand/dirt, wouldn't it be dispersed more randomly when I find it. This stuff seems to collect in the same general areas (though with that said, perhaps my pool's circulation could be the culprit).

How fast does algae grow overnight at a FC 15ppm?
 
I know that the swim season is pretty much over at this point. I suggest an OCLT test to determine whether you have pollen or algae, but your test kit can't measure FC levels higher than 15. http://www.lamotte.com/en/pool-spa/labs/3576.html It is best to do the OCLT at shock levels, but your kits can not accuately test FC . With a CYA of 85, your non-shock FC target level is 10 and you should never let your FC get below 7 and your shock level is 33 per pool math.

You could purchase the taylor FAS/DPD powdered chlorine test so that you can test your FC at higher levels. This test is $26 from TF Test kits: http://tftestkits.net/Individual-Tests-c6/ But the value is in the full test kit which could get your through two full seasons (and the rest of this season).

Overnight Chlorine Loss Test: http://www.troublefreepool.com/content/136-perform-the-overnight-fc-chlorine-loss-test-oclt

You could skate by and hope that some of your CYA goes down over the winter. I happen to have the magical substance that eats my CYA each winter. The winter drain/refill process could help you get to a more manageable CYA level next year.
 

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pisymbol said:
I did try to pick some up, it didn't feel overtly slimy but it also didn't feel squishy. But if it was sand/dirt, wouldn't it be dispersed more randomly when I find it. This stuff seems to collect in the same general areas (though with that said, perhaps my pool's circulation could be the culprit).

How fast does algae grow overnight at a FC 15ppm?
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If it's dust-like and goes into a cloud in the water so is hard to pick up AND if it's only in shady areas and not anywhere where there is mostly continual full sun and if it's yellow/mustard in color, then it's likely yellow/mustard algae. Sand/dirt and pollen would accumulate where the circulation tends to deposit it, but sand/rocks would be hard and move but not poof up. Pollen would tend to resettle as well. Finer dirt could poof up and disperse but doesn't care about sunny areas and usually isn't yellow/mustard in color (it's more brown).

When asking about algae growth, the FC is completely irrelevant by itself because most chlorine is bound to CYA. It's the FC/CYA ratio that is relevant and with a ratio of 7.5% or above then green and black algae cannot grow (the ratio is 5% in SWG pools), but with yellow/mustard algae it takes a ratio of 15% to stop its growth which is why we recommend eradicating it completely. However, you may also have poor bottom circulation so the chlorine level may not be as high at the bottom of your pool.
 
chem geek said:
If it's dust-like and goes into a cloud in the water so is hard to pick up AND if it's only in shady areas and not anywhere where there is mostly continual full sun and if it's yellow/mustard in color, then it's likely yellow/mustard algae. Sand/dirt and pollen would accumulate where the circulation tends to deposit it, but sand/rocks would be hard and move but not poof up. Pollen would tend to resettle as well. Finer dirt could poof up and disperse but doesn't care about sunny areas and usually isn't yellow/mustard in color (it's more brown).

When asking about algae growth, the FC is completely irrelevant by itself because most chlorine is bound to CYA. It's the FC/CYA ratio that is relevant and with a ratio of 7.5% or above then green and black algae cannot grow (the ratio is 5% in SWG pools), but with yellow/mustard algae it takes a ratio of 15% to stop its growth which is why we recommend eradicating it completely. However, you may also have poor bottom circulation so the chlorine level may not be as high at the bottom of your pool.
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I got you. I now understand the relationship between CYA and FC. 30ppm is a bit excessive. Should I drain the pool via backwashing and then refill and retest my CYA? The idea is that I can reach a much more sustainable FC level than the one I need now.

About the algae, and chemgeek this is what is driving me nuts, my pool has FULL SUN ALL DAY LONG. There is no shade. And the algae or dirt or whatever still accumulates. That's why I'm confused.

EDIT: Bought TF-100 with SpeedStir.
 
The south wall/floor of your pool should be in the shade most of the day because the pool wall itself shades these locations. Is that where you see the "algae"?
 
mas985 said:
The south wall/floor of your pool should be in the shade most of the day because the pool wall itself shades these locations. Is that where you see the "algae"?
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Honestly, I see most on the low end side where there is the most direct sun light. That would be North.

Not that there isn't anything on the South side, but the most amount of "algae" is on the North side.
 
pisymbol said:
Honestly, I see most on the low end side where there is the most direct sun light. That would be North.

Not that there isn't anything on the South side, but the most amount of "algae" is on the North side.
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That's interesting and makes it less likely to be yellow/mustard algae. You might get a skimmer sock to put over the skimmer and see if you collect anything that looks similar. If you do, then that's falling into the pool (could be pollen) and some is sinking to the floor and not getting circulated or caught in the filter. That would also be consistent with the fact that the SLAM didn't kill it.
 

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