Penn-Plax
Penn-Plax Premium Under Gravel Filter, 20-Gallon
Tetra
Tetra Aquarium Power Filter, Whisper EX30 for 20-30 Gallon Fish Tanks
Aquaclear
Aqua Clear A595 - Fish Tank Filter - 5 to 20 Gallons - 110v, Black
Coral Farmer
Slim Power Filter S20 for Aquariums up to 20 Gallons