This filter should use with air pump, air pump is NOT included here. Sponge filters provide both mechanical and biological filtration. Simply install an airline into the unit and provide both aeration and filtration for your fish. Aerobic bacteria colonize the sponge providing a bacterial substance to facilitate the nitrogen cycle. ou can use the corner sponges for a good few months before needing to use replacement sponges. Use water from the aquarium to rinse off the sponges instead of tap water. They are useful for as breeding filter or as secondary filter. Or they can be used as pre-filtration unit by fitting to an external or a top filter.