CYA over 100 with yellow/mustard algae

I'm glad to here you're going to try it; I'm really excited to see what happens.

Regarding mechanism -- phosphate is simply one of the key plant fertilizer components. If you garden (or farm), you've seen fertilizer ratings, like 10-10-10. These are NPK -- nitrogen/phosphate/potassium -- ratings and report the relative percentages of those plant nutrients in the fertilizer. You can use soil tests to find out if your soil needs more of one or the other nutrient, and match the fertilizer to the need, for example, applying 20-5-5 instead of 10-10-10.

Adding fertilizer, to match soil deficits, or crop needs, is what you do when you want plants to *grow*. Using phosphate remover is what you do when you do NOT want plants (algae!) to grow. Essentially, you are trying to remove, almost completely, a key plant nutrient: phosphates.

Please note that phosphate removal does NOT kill algae; it just makes it unhealthy and weak. You STILL have to chlorinate to kill it, but with low phosphates, it's much harder for the algae to recover from chlorine damage.

On many (most?) pools there's no need for this: chlorine destroys the algae just fine without weakening it by creating a phosphate deprived environment. But, some pools recurrently harbor chlorine resistant algae,

Why? I don't know!

But, on at least one such pool (the large country club pool I service), removing phosphates has resulted in substantial changes in the 'health' of the algae present. I don't yet know if this pool has previously had unusually high phosphate levels, or not. But I do know that with very low phosphate levels, the resistant algae this pool has ALWAYS harbored is not growing, and chlorine demand is way down.

I'm hoping that your pool, which has apparently also suffered recurrent mustard algae IN SPITE of high chlorine, may proved to be a second case. I'd *love* to be able to selectively recommend phosphate use, if it solves the problem some users have with recurrent algae.

My pool also has had recurrent mustard algae problems despite high chlorine levels. I've kept it in check with slightly elevated FC and regular use of my robotic cleaner. Last year the robot failed and I went with brush and vacuum. The Yellow Beast started appearing in corners, liner seams and depressions in the floor. Several weeks of ++SHOCK++ levels and daily brushing didn't eradicate it.

My pool has solar panel heat and I use a solar blanket to retain heat. These may contribute to my difficulty removing the Mustard Algae.

I'd like to join this phosphate removal study this summer as well (now the pool is ice) - if I may.

Should I start a new thread or keep this all together here.

By all means, please do. I'm particularly looking for people with some testing experience, so we can get a better idea of what's going on.

Let's keep the discussion altogether here, for now. If it's needed, I can pull apart the posts into two threads.

I'm absolutely fascinated! For years we've railed against pool stores selling "Phosphate Reducer" and worse, annual contracts for it--as mainly a waste of money and had scads of pools with "high phosphate" levels that never had a problem.

Now we have a workable, truly testable hypothesis: that when a pool is suffering from Mustard algae, phosphate reduction may actually BE the way to finally solve it! If this turns out to be true, we will have another simple, clear-cut tool in our tool-box!

Since my pool is still a skating rink under the cover (despite warm days we are still waking up to the 'teens') I won't be much help in testing! :)

As for the Borates not helping, this link gives some info on borates inhibiting algae growth. The algae listed are Scenedesmus quadricauda, Scenedesmus subspicatus, and Microcystis aeruginosa, where the first two are green algae and the last one is a type of black algae. Though there are many types of algae, the three main groups we describe for pools are 1) green algae which are plants in the phylum Chlorophyta which contain chlorophyll a and b, 2) yellow/mustard algae which are in the kingdom Chromista (e.g. phylum Heterokontaphyta class Xanthophyceae with a cell wall of cellulose impregnated with silica) which contain chlorophyll a and c, and 3) black algae which are in the phylum Cyanobacteria (sometimes called blue-green algae but they are not plants) which contain chlorophyll d and/or f. 50 ppm Borates has roughly 50% or more inhibition against green algae, a small uncertain amount of inhibition against black algae, and an unknown inhibition against yellow/mustard algae. Given how yellow/mustard algae is generally more resistant to chemical attack in general, it is not surprising that the borates are not very effective against it.

OK, I got the Taylor K-1106 phosphate kit. The pool water is indeed high, around 800 ppb. I tested 3 times... once diluted, twice non-diluted, and results were consistent. However, the tap water is zero... no hint of blue whatsoever in two non-diluted tests. So, I'm not sure what the source of the high phosphate would have been.

In any case, I have now ordered the Kem-Tek 265-6 phosphate remover and I'll begin dosing after I receive it.

FYI, I've been maintaining FC at 20+ for the last 5 weeks, and this is with relatively low CYA of 32. Daily consumption averages around 3 ppm. After brushing, the algae returns to the same spot about 2-3 days later, without fail. Here are the rest of my current numbers:

FC=20.5
CC=0
pH=7.7
TA=75
CYA=32
CH=260
Borates=50

Thanks again,
Mike

Interesting. That pretty much rules out borates as having much impact on mustard algae. It's also amazing that you're having recurrent algae with FC=20 and CYA only 30 ppm.

I have to say, that while I'm sorry for your problems, I'm glad for the opportunity to test this out. The fact that you have no phosphates in your tap water certainly makes things easier. You will need to practice extreme vigilance in what chemicals you use, and avoid using ANY products made by United Chemicals, as well as most stain/scale products. You probably want to avoid clarifiers, flocs and any other 'enhancement' products.

But even there it will be interesting to track your phosphates, to see what makes them rise, after you lower them.

Thanks so much!

Big Dave's Mustard Algae Experiment contribution:
I took the cover off March 26 and topped up.
After adding water, the FC was 10.5, CC 0.0, CYA < 30, and pH 7.4; temp. 64 F. No sign of mustard algae.
Over the next three weeks, I chlorinated with a total of 5lbs of dichlor keeping the FC at 15-20.
The pool collected quite a bit of debris during this period that I vacuumed into the filter; Backwashed on June 15.
June 16, FC 8.0, CC 0.0, CYA 70, pH 7.4, TA 80, CH 11, borates 30; temp. 78 F. No sign of mustard algae.
June 17, FC 7.0, CC 0.0, pH 7.4; temp. 83 F. No sign of mustard algae. We took our first swim - Yay!
June 18, FC 5.0, CC 0.0, pH 7.4; temp. 88 F. No sign of mustard algae, Kids swim. Added Bleach.

I'm not sure If I'll be a good case - time will tell. I've disposed of our old solar blanket that I suspect was harborage for the algae.
With the K-1106, I measure > 1000 ppb phosphate in my pool and 500 ppb phosphate in my fill water.
I have 2 quarts of Kem-Tek phosphate remover on hand and plan to bring the phosphate to 100 ppb.
I also plan to buy a new solar cover in July - We'll see if that brings the yellow back.

Hi all. OP here, with an update. As posted before, my phosphate was quite high, in the 800-1000+ range. I ordered 2 quarts of the Clorox phosphate remover as suggested, and added it slowly over a couple weeks. No problem with the filter or clouding. But zero impact on phosphate level also. Still very dark blue using the K-1106 kit. I waited 2 weeks after treatment to re-measure. Very disappointed in that product.

Needless to say, I still have the mustard algae. It comes back every 1-2 days after brushing. With the very hot temps here in North Texas, it's been a little worse than usual.

Anyway, I'm looking for new suggestions on a phosphate remover that actually works, so we can continue this experiment. My local pool store has several products, but I'll defer to the experts here.

Thanks,
Mike

P.S. I've been maintaining FC in the 6-10 range. Here are the latest numbers:

FC=9.4
CC=0
pH=7.7
TA=75
CYA=37
CH=230
Borates=50

The Orenda PR10,000 is one effective product and reasonably priced for the amount of phosphate it removes. A pint is around $25 and will remove 5000 ppb per 10,000 gallons so should be more than enough for your pool.