Penn-Plax Clear-Free Undergravel Filter

For 15/20H gallon tanks  - 11 1/2" x 23"
For crystal clear water at a great price.
Biological filtration with replaceable mech anical  filtration filter cartridges.
Works with any standard air pump.
This is a two plate system.
Two lift tube design.
Can run easily with powerheads.
Great for fresh and salt water fish.