Keep your aquarium free of harmful ammonia and your multi-stage mechanical filtration operating effectively with Fluval C3 Ammonia Remover Filter Media. Fish waste， uneaten food and other refuse can cause ammonia to build up in your aquarium which can cause stress， illness and even death. Fluval C3 Ammonia Remover Filter Media works in Stage 3 and immediately removes and controls ammonia and nitrite， improving your water quality and reducing stress on your fish. It is ideal for new or heavily populated freshwater aquariums.