I went online and purchased a 10 gallon water cooler from Lowe's to store my fresh water for top offs. Since I don't have the room for a ATO system (space is limited) and I don't have an RO/DI system I use the API Tap Filter which has been great for me. Once I do this, I still add some Prime to make sure. Since I have done this, I have noticed a huge difference compared to me using tap water with Prime in the tank. I have a FOWLR 36 gallon tank and usually have to add about 1 gallon every 3-4 days for top offs. So since I have to pull out and hook up the API Tap Filter each time, I usually would store them in six 1 gallon jugs but with this cooler I have 10 gallons and that should last me an entire month of top off. The best thing is the regular price for the cooler is over $49 but if you buy it online now you can get it for under $13: Shop Igloo Blue Poly Beverage Dispenser at Lowes.com Now I have all my top off water stored in the garage in the corner with this cooler. It makes it easier for me to store instead of pulling out these bottles each time!