Just to pass a little advice on to some of the newbies such as myself, as you may have read in the sick fish section I have a case of Velvet and I'm not out of the woods yet but without a Rodi unit on hand for water changes and xtra water for the qt tank I would have lost every fish i had, not saying I still wont but at least I have a shot of curing them and without a ro unit they would all allready be dead. I have used 60 gallons today alone and a lot more needed in the next few weeks. This happened to me on a sunday night when all stores were closed and today was a holiday with most stores closed. Without a unit I would have had no water today. Something to think about for the future and believe me when i say this can and probably will at some point happen to you. I hope it doesnt but you never know.