20i: Aquariums up to 20 Gallons, 125 GPH, Large Bio-Bag. 4.9"L x 5.4"W x 10.2"H. 20i (20 Gallons). Tetra Whisper In-Tank Power Filters provide the ultimate in convenience and quiet. These filters mount on the inside of the aquarium, rather than hanging from the outside -- making it possible to place the tank flush against a wall.
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