Bio-Sponge Filter offers effective mechanical filtration that rids aquarium water of waste products, while adequately oxygenating the water The foam construction also acts as biological filtration and offers an environment that encourages the colonization of good bacteria Suitable for use with an air pump or an external filter The Tzong Bio-Sponge filter operates silently, and is easy to install and maintain Double 10-layer ribbing shape sponges design that quickly established a bio-filter and extra oxygen Two sponges mean more surface area for beneficial nitrifing bacteria to colonize and faster cycling, keeps your fish tank water super clean and crystal clear Comes with 2 suction cups to stick to glass, can be installed anywhere It can also be used as a prefilter or secondary filter Perfect for shrimp tank, betta tank, breeder tanks, turtle tank, goldfish, discus, crayfish, fry, baby fish or other fish