Features:

Biochemical sponge filter provides biological filtration to the aquarium, helps to stable water quality.

Increase the oxygen solubility in water.

Working noiselessly.

Good permeability, easy to clean.

Perfect filters accessories for your tank and aquarium. 
If the filter is without filter balls, it may float on the water. So filter with balls is recommended.

Speicificaitons:

Product name: Aquarium Sponge Filter

Color: Black
Size for filter: 6cmx9.6cm for small size,9cmx15.7cm for medium size.
Reminder:

1. Soak the sponge in the aquarium water for 5 minutes before use, by doing this will help nitrifying bateria colonise easier.

2. Always use aquarium water under room temperature to rinse clean the sponge, never use hot water.
3. It must be used through connecting the air pump.

4. Squeeze the sponge repeatedly to expel the air so that the filter sinks to the bottom of the tank when put the filter in water.

Including:
1pcs Aquarium Biochemical Sponge Filter/2Pcs Sponge