Nutrifield® pH Up & Down are tank controllers that will assist in reaching desired pH levels. The pH scale measures how acidic or basic (alkaline) a substance is. It ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic, and a pH greater than 7 is basic (alkaline). Plants thrive in a pH range of 5.5 to 6.5. When monitoring your reservoir or tank, you should always check your pH levels to ensure that you stay within an acceptable range for your plants. Nutrifield® pH Up & pH Down are essential tools for you to use to keep your nutrient solution balanced.