How often should I change my reservoir water?

We recommend changing out your reservoir water completely every 7 – 10 days. Even though you can top off evaporated water by measuring and not exceeding overall PPMs, you can’t measure the ratio of different nutrients left in the water after plants have used part of them up. (For instance, plants may need / deplete more nitrogen during some growing stages.) The only way to ensure optimal growing success is to know exactly the ratio of NPKs you’re feeding by starting fresh with a fresh batch of nutrient solution.