An "as-needed" chemical. If water is cloudy, it may be due to thousands of small particles (bacteria, dirt, and other debris) that are suspended in the pool water. These particles are so small that they escape both the chemicals and the filter. If this is the case, a Clarifier is used to restore water clarity. Clarifiers are liquid. Read the instructions on the label to determine the amount to add, how it should be added (either diluted in water or poured straight from the bottle), and if it should be added before or after shocking the pool; clarifiers are often used in conjunction with shock to restore water clarity.