Penn-Plax Clear-free Air Cartridge Filter 2 - up to 20 Gal.

The Clearfree II is a precision, made to fit corner filter.The filter is easy to set-up and maintain. It provides triple action filtration. The filter cartridges contain dacron floss for mechanical filtration, a foam pad for ammonia-removing biological filtration, activated carbon for chemical filtration and zeolites for removing ammonia. The filter is operated by an airpump (not included). The included airstone omits bubbles that allow the water to flow through the filter cartridge. The corner suction cups allow the filter to fit with precision in the corner of your aquarium.