“pH Test Kit or Reader: You can purchase a set of pH test strips for $10 off Amazon. These allow you to check the pH level of your nutrient solution by seeing what color the strip changes to. Similar to the pH Test Indicator of the last section, these are important to have on hand, but they can start to get costly if you have a lot of checks to do. Replacing the pH Test Indicator or your pH stripes could easily run you $50 or more in the course of a year.”