Drops are reliable and simple to use. Fill the test tube about halfway with the nutrient solution, then add a few drops of the pH test indicator and observe the resulting color. Red (acidic) indicates that the pH is too low, blue (alkaline) indicates that the pH is too high, a yellow to a yellow-green indicates an ideal pH. Comes with an easy to match pH color chart. This item is the perfect back-up to a digital meter.