Keep your fish healthy and breathing easy with the JBJ Aquarium Rimless Desktop Bio Aquarium Filter Media Replacement! It fits the JBJ Bio Aquarium Filter (sold separately) and helps remove bad bacteria in your aquarium. Designed as replacement filter media for the desktop rimless series of tanks (each sold separately)， each pack offers four changes. All the media for your tank is included—fine sponge， coarse sponge， activated carbon and ceramic rings—which is all the mechanical， biological and chemical filtration media needed for your filter. This filter media fits perfectly into the JBJ Bio Aquarium filter caddie (sold separately) for easy replacement. You’ll love that your aquarium will stay crystal clear while maintaining good bacteria. Just remember that even though the media comes packaged together， don’t switch out all of it at the same time or you risk losing too much of the beneficial bacteria in your aquarium. Your fish will thank you!