Another note . . . phosphate removers can probably remove phosphates down to any low level you can measure at pool side, and such low phosphate levels will inhibit (not totally prevent) algae. However, what pool stores don't tell you is that many common pool chemicals CONTAIN phosphates! We've had several pool store 'prescriptions' posted this year which contained BOTH phosphate removers AND phosphate based, or phosphate containing, products.

Given your persistent upward trend on phosphate levels, I'd wonder just what ELSE your pool store is selling you. It's quite likely they are 'helping' you remove phosphates on the one hand, and then 'helping' you add them back* on the other! If you want to know, you'll need to list the EXACT product names of everything you've added since the last low phosphate reading.

Ben


* To be fair, the only thing about pool chemistry most pool store operators know is what they are told by pool chemicals companies, and, as you might imagine, this little titbit is not usually part of such training!