I used Poly 60 for the first time on 6/29. First the initial recommended dose on day one and a weekly maintenance dose on 7/6. It’s done an amazing job clearing up the nuisance bottom algae on the gunite, but now I’m getting copper readings for the first time ever. .1 on 7/2 and .4 today. Poly 60 is supposed to be copper free, so I’m wondering what’s going on. Pool is crystal clear.