Tetra Whisper PF10 Power Filter, Quiet Three-Stage Filter 5-10 GALLON AQUARIUMS: Designed for use in smaller aquariums up to 10 gallons. USES MEDIUM CARTRIDGES: The Tetra Whisper PF10 uses medium Whisper Bio-Bag cartridges. Replace cartridges to keep your filter functioning properly. THREE-STAGE FILTRATION: Keep cleaner water and healthier fish with three-stage filtration.