Use these pH tester/monitors to test the pH level in your soil, hydroponic / aeroponic reservoir or nutrient solution. pH (potential hydrogen) measures the acidity or alkalinity of your solution on a scale of 0 - 14. A solution is considered acidic below 7 and basic at 7 or higher. When working with hydroponics you typically want your pH to fall between 5.8 and 6.2. When growing in soil or coco you want your pH between 6.0 and 6.8. The most important rule to remember with pH is to avoid extremes. Nutrient "lockout" occurs with high and low pH levels