I looked at other places for RODI
units and they were moderate to expensive in price. In the long run it does save you money and time as using RODI
water will help you keep phosphates down. Just for the sake of comparison, use a test kit and test the phosphate levels in your tap water. I think you will be surprised. Getting rid of algae is a real pain if you get it and takes time. This is not to say you won't get algae ever however it does help!
In addition, if you ever decided to add corals etc., you would need one.