Are you brushing the pool?

Physically disturbing the algae is necessary to break up the protection layers that the biofilms create. Other than consistent high chlorine PLUS brushing, the other treatment options are not super attractive.

=> Copper algaecides, at high doses work. But they also stain and turn hair green.

=> Ammonia based mustard products also work, but leave you with a downstream clean up mess -- very high combined chlorine.

The remaining option is what I'm currently testing: very low phosphate levels. But there are games going on with the concentration of the products. Currently, the only reliable product seems to be the Orenda PR-10000 product, which is not widely available. None of the major online distributors have it, probably because it makes their favored products look bad. Here's a listing from Google Shopping.

To use it, you ALSO have to get the Taylor K1106 Phosphate kit . But it appears you haven't even gotten a K2006 . . . so for whatever reason, so I'm guessing this is not an option for you.

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I think we're out of options here. I'll admit the choices aren't great, but they are what they are, and talking about them longer isn't going to change anything. Honestly, if your budget is too tight to allow you to get a K2006, it's probably too tight to deal with mustard algae, no matter what direction you go in.

You may be better off simply covering the pool, and adding chlorine underneath. After a couple of weeks at 20 ppm and no light, the algae will almost certainly be dead.

But I think we've done all we can do.

Sorry!