Maintain a healthy aquarium with the Top Fin Filter Cartridges. Filtration sponge with activated carbon helps keep water clear. Thecartridge is easy to remove and replace. Only atPetSmart. Features: Easy to remove and replace Includes: 2 AAA" Filter Cartridges Caution: This is not a not. Keep out of reach ofchildren. Advice of Use: To help maintain a healthy aquarium, change the filter cartridgeevery 3 AAA" 4 weeks. Remove the cartridge when medicating the wateras carbon will absorb medications. Change out 10%of the waterweekly or 25% monthly. Use a water conditioner every time you addfresh tap water to aquarium water. Never use soap, detergents orcleaning agents while cleaning aquarium or equipment as they canharm your fish. Directions for Use: 1. Rinse the filter cartridge under cool tap water to removedust. 2. Insert the cartridge, opening side up, into the frame(includedwith the Top Fin Multi-Stage Internal Filter).