Posting new thread per @mguzzy:@MarieB ... White flakes from your SWG means your CA is high and your CSI is allowing it to deposit. You should start a thread on that and we can help you get that under control. If you have high CA in your fill water running it through a water softener (if you have one for your house) will help.
I was trying to find a sequestering agent that I could also filter out.. hence the use of MM.. but it appears to be not a complete solution. I am now convinced the surest way to get the iron out of a pool water is with a drain/refill. I think I will try a few staged drain and refills during our rainy season. I just hope it rains this year.
My csi has been within optimal range and I am getting white flakes out of my returns, as generated by SWG. Pool store states calcium hardness at about 440 or so. My fill water is about 200-250 if memory is correct. Replacing evaporation loss always adds more CA. Too expensive to drain and refill, can only refill every five years. I am trying to vacuum out and net out the white flakes, hoping that will make some degree of difference. I do not have a water softener. If my csi is optimal, then the CA won’t attach to surfaces, is that correct?