All I have right now is a 2 stage unit haha. Not even R/O. Well, it may be. I am looking for something because I have spend over $3000 in less than a week on fish stuff and my wife is kinda well not so happy. Which I can understand. But, I need a good R/O unit before I fill this bad boy up. HAHA maybe I can barrow a friends. That is sad hu? I will get a good one in a few weeks.