No I leave the sponge blocks in place but I use a sponge block as a pattern to cut out 3 slightly over-sized (for tucking in top bottom and sides) Poly-blanket rectangles to place in front of each and every sponge. If you feel your poly blanket is too thick like mine, they will also pull apart right down the middle so that 1 rectangle makes 2 Poly inserts. Works great. This also helps seal any Bypass around the individual sponges. Make sure there are no loose dangling ends that can obstruct the inside channel where the water continues to the top central media basket and flows down against basket media in the correct direction, unlike all other inline basket filters on the market which flow from the bottom up lifting media off their basket grates and bypassing unfiltered water back to tank.so CWO4GUNNER you put your polywool in where the foam pads would go on the 1st basket? and just use the foam in the 2nd and 3rd baskets?