I use to buy all that filter pads, filter socks and other expensive crap... I switched over to Walmart poly fill and I'll never go back. Working on new tanks and filter setups and planning involves how to house the poly fill for easy maintenance. $8 last me about 4 months and I still have half a bag. And I switch out every week.Replacement filter pads can be made out of quilt batting from walmart. About as cheap as you can get