The Odyssea Hang On Power Filter 50 provides mechanical, chemical, and biological filtration for 20 - 50 gallon, salt or freshwater aquariums.  It is economical and easy to use.  Featuring 3-in-1 cartridge which comes with the filter for your first time use, has large surface area to trap debris and waste retention, helps eliminate odors, and promotes beneficial bacterial growth.  Extra filter cartridge slot to maximize filtration power.