Keep your aquarium clean and healthy by growing beneficial bacteria with Fluval C2 & C3 C-Nodes Filter Media. One of the most important ways to maintain good water quality and keep your fish thriving is seeding your aquarium with good bacteria. This bacteria breaks down harmful ammonia from fish waste and other organic matter and starts the aquarium nitrogen cycle. Fluval C2 & C3 C-Nodes Filter Media have a complex pore system creating an optimal environment where this beneficial bacteria can thrive. These small， star-shaped filter media have a higher filtration surface and more capacity than most biological filter media， reducing and controlling ammonia and nitrates.