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.