We have many customers who use our polishing pad in their hang on the back filters. Since the polishing pad has a very tight fiber network it will slow the water flow down. Obviously as it traps debris the water will continue to slow. The polishing pad should be used after the water flows through a filter cartridge or filter pad like our Premium dual density pad. Theses pads will remove most of the larger debris keeping the polishing pad from clogging up to quickly. The benefit is our polishing pads do produce super clear water.