Hi! I use strictly rain water collected from the house roof drain system. I filter out particles with a cloth strainer. I raise West African dwarfs and Corydoras. I think this is the best alternative to ro. I have no city water and use the rain water for the house, but since it is held in a large underground concrete tank the pH is a little high. The rain here in KY is pH 7.0 . I find the dark blue 55 gallon plastic barrels are the best and retard algae with their dark color. Mike