Aqueon Filter Cartridges are replacement cartridges for the Aqueon hang the back QuietFlow filters.
Small Cartridge: For Aqueon Mini-bow tanks
Medium Cartridge: For Aqueon QuietFlow 10 Power Filter
Large Cartridge: For Aqueon QuietFlow 20, 30, 50, 55, and 75 Power Filters
Rivers to Reef say: Please make sure to get the correct size for your hang on the back filter. Each manufacturer makes a different shape, so these would not work for a Whisper filter. Typically cartridges last about 4 to 6 weeks.