I am getting a lot of different info on this one. All of the breaders I have talked to tell me not to mess with RO. They say Tap is more stable and once the fish are aclimated to it there is no problem with keeping them in tap at all. My tap here is not that bad. (The only exceptions is for hatching eggs which I wont be doing). However a lot of what I read says low PH is best for discus and RO water is great. It is true that the fish we keep now are not like the ones captured and kept 20years ago, think about it they have bin tank raised for generatons (mostly). SO what do you guys think? I am looking for your Thought's on this and your experiances. Thanks, Arkangel77