Personally I would buy R.O. water form any store. I know 2 LFS in town that doesn't change filters but once a year. R.O.'s are cheap if you break it down. It cost about $.01 to $.02 per gallon. I use mine for drinking water too. out here is cow country not as bad as dakar and reef angel but still bad. They have a little more pos. and nitrates up there. Either way if you own a tank I always recommend a R.O. with two D.I. I think that would be a great artical for everyone to read. Would you guys like to see if I can dig it up?