(Ship from USA) Aquapapa 4x Bio Sponge Filter Betta Fry Aquarium Fish Tank Double Sponge (S) XY-2831 .ITEM-NO/EGB41S-1GFT10832 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. The sponge traps larger waste particles mechanically cleaning the water without trapping baby fish. Product dimensions: 5.0"L x 1.8"W x 5.5"H; sponge dimensions: 2.4"D x 4.5"H. 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.