For Sand Filters Only. Clarifying Tabs are specially formulated tablets that dissolve in the skimmer, releasing a clarifying agent that traps in the sand bed of a sand filter, dramatically improving their ability to catch particulate and waste that makes water dull and cloudy. Very easy to use, just drop in the skimmer basket. Ideal for use as a general filter aid that is added after every backwash or as a special problem-solver when water goes cloudy after an algae treatment, excessive pollen build-up or other like problem.