I bought this to make distilled water for my nano shrimp tanks. I had been buying gallons of distilled water from the store. Now I just run it and fill my empty jugs so that I always have some on hand for water changes. There are no copper pipes which was important to me as copper can poison my shrimp. I bought additional citric acid from Amazon for cleaning. Probably not practical for large aquarium water changes, but mine are only around 3 gallons each and this works perfectly! Gets the TDS down to almost 0ppm. Then I add back what I need to, or don't add any minerals at all for tank top offs. Very happy with this machine!