Function: The Aquarium Air Driven Bio Filter Sponge can efficiently remove waste and maintain clean water for your fish. With multi-layer sponge filters, this filter combines physical and biochemical filtration for your fish and increases the oxygen solubility. Unique Design: The multi-layer shape increases the area to get a better water and oxygen exchange rate. It also makes the filter easy to hide in the corner of a tank. Easy to Use: Just take out the Filter Sponge and rinse well when it becomes dirty. Soft sponge material, traps floating debris and 't suck up your fish, excellent for small size fish like , dwarf cichlid, guppy, killifish etc, or for hatcheries, maternity tanks, and fry tanks. Notice: Each Aquarium Bio Filter Sponge requires an air pump and air tubing to operate together. So, it can't work separately. Colour:Black & White Material:Sponge + plastic Size:Total height: about 8cm cotton size: about 4.5x2.2cm Package Contents: 4 * sponge filter Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.