Hello, I am very very new to this forum and very new to pools as I just bought a foreclosed house with a very stained pool. The pool stains are black/brown/orange which after reading these postings make me believe that they are from metal. I have brushed with a metal brush for 3 weeks now and nothing. I want to try MBAR's Ascorbic Acid Treatment, but I have a cartridge filter and I don't know how to turn the filter off and "circulate" the water. Will the treatment work without turning the filter off? Please help. Thank you so much!!!!