This is why I needed to add an RO filter for my aquarium fill water… this picture is my hard water tap, before my RO unit… I can use it to blend in some hard water if desired… I don’t currently add any to my fish tanks, but my Cherry shrimp tank gets just the hard water… this staining of the lines, resulted after only 6 months, and is only used to maintain 1 - 10 gallon tank… also why I’m building a manifold to get RO water to the tanks in 2 other places in the house
