General Hydroponics pH Control KitDial In Your Plant Nutrition With The General Hydroponics pH Control Kit Testing the pH of your nutrient solution has never been easier. This is an essential task for growers, because plants need a very specific pH range: between 5. 5 6. 5. When you extend above or below this range, certain nutrients start to get locked out, and your plant will develop nutrient deficiencies. By the time this happens, it can be tricky to determine what the root cause