Penn Plax CPF5C Cascade 300 GPH Hang On Aquarium Filter Cartridges with Activated Carbon; 1 Pack 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. 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. Perfectly measured to fit into the Cascade 300 filter tray without any gaps preventing debris and contaminants from passing through back into the water.