Keep your tank clean and clear with the genuine Penn Plax filter cartridge to fit your Cascade 300 GPH hang-on power filter model CPF5. Sold in 3 pack.Activated carbon is great for freshwater aquarium filtration.  It has the ability to remove odors, and water discoloration by trapping the pollutants in the pores of the carbon.The poly-fiber floss barrier screens out particulate matter and debris keeping the water clean, clear, and healthy.No assembly required keeping your hands clean. Easily install into interior compartment of your hang on filter. Suitable for freshwater and saltwater tanks.Internal filter cartridge comes in either Blue or Black plastic - and both are identically measured to fit into the Cascade 300 filter tray without any gaps preventing debris and contaminants from passing through back into the water. The Penn Plax Cascade 300 GPH Filter Cartridges with Activated Carbon will improve the quality of your aquarium water and keep your fish healthy.  This replacement filter is designed to fit your Cascade 300 GPH hang-on power filter and will last 6 to 12 weeks under normal conditions.  Activated carbon is great for freshwater aquarium filtration.  It has the ability to not only visually clear the water, but trap pollutants in the pores of the carbon so they do not enter the water.  This filter cartridge will remove ammonia, nitrites, odors and other harmful toxins from your aquarium to keep it healthy. It has a poly-fiber floss barrier which screens out particulate matter and debris for an extra layer of protection. Within 24 hours you will see a drastic difference in the water quality.  Each filter cartridge is perfectly measured to fit into the Cascade 300 Hang on Filter tray without any gaps preventing debris and contaminants from entering back into the water. This filter cartridge is suitable for both freshwater and marine environments. When used together, the Cascade 300 GPH Filter Model CPF5 and Cascade 300 filter cartridges provide maximum protection against water pollutants from harming your fish. Sold in 3 pack.