I use some I get from Home Depot . They are in the pond dept . A 2 pack is about $10 , but I cut them in half so I get 4 . I like them because they are fine enough to catch debris , but coarse enough that they don't clog so fast . I rinse them once a week at WC
's , but could go longer . I just do it while I have the filters off for WC
. They do have a hole all the way through , but I just cut a small piece of any kind of scrap sponge I have and stick it in the end . If they are too big just use a rubber band to keep it on . I use them on some Marineland filters that have big intakes and I can get them to stretch over with a little effort .