The compact h 2 phase bio internal filter requires the following filter media poly pad carbon sponge filter sponge coarse filter sponge fine zooplus brings you all of these in a convenient set 1 pack of poly pads 5 1 pack of carbon sponges 2 1 coarse filter sponge 1 fine filter sponge poly pad poly pads are designed to absorb larger particles of dirt in the water when the particles are caught by the pads they are prevented from obstructing the growth of water cleansing bacteria change