I just have my unit hooked up to a faucet in my utility sink. I keep (4) 5 gallon buckets filled all the time which I use for top off water or water changes. I then turn on the faucet to make more water and refill my buckets. I have a 72g and a 180g which are both fish only. I really don't know much about the 9 stage units except that they process more water faster. You can add chemicals to tap water, but still not the same as R/O water, especially when it comes to algae control. I use to use tap and have found a BIG differnence since I have been using strict R/O water. The tank just stays cleaner looking longer and the PH seems to keep stable a lot easier.