CYA over 100 with yellow/mustard algae

[MikeM]

OK Ben, I'm game. I just ordered the Taylor phosphate kit. I'll hold off on the remover until I confirm my readings. I'll post my readings from the pool and tap after I get the Taylor kit.

Meanwhile, can you explain the cause-effect relationship between high PO4 and yellow algae? Or just refer me to some additional reading material?

Thanks,
Mike

[PoolDoc]

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.

[BigDave]

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.

[PoolDoc]

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.

[CarlD]

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!

[chem geek]

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.

[MikeM]

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