Hi everyone, I apologize for my terrible English, my name is Francesco and I am Italian and I live in Italy. I also wrote in your forum last season as I had problems with iron stains (even if I use mains water with low iron values) I tried ascorbic acid and oxalic acid last season, the stains disappeared but I had big problems with the chlorine level and as soon as I started to slowly add chlorine the stains came back. speaking with a technician it turned out that the problem is the iron bacteria in the pool and this year I decided to empty the pool (250 cubic meters), clean it completely with acid and after filling the pool before starting to add chlorine I used copper pentahydrated on the advice of a technician to kill the iron bacteria present in the water but when I started using chlorine the stains started to reappear (although in much smaller quantities than last season) does anyone have any new advice to give me? the same technician advised me to use oxalic acid in very small quantities (only on the stains), do a new copper treatment and then treat for a period only with active oxygen. Do you think that active oxygen could be a good solution?