Aquaclear 20 Replacement Media Bundle: Sponge, Carbon, Ammonia Remover Bundle includes: Ammonia Remover, Activated Carbon, and Foam Filter Inserts All inserts are custom designed to fit the AquaClear 20 aquarium filter Activated Carbon improves water clarity in fresh and saltwater aquariums Foam effectively removes particles and debris from aquarium water and provides powerful biological filtration Ammonia Remover controls harmful ammonia and nitrite, creating a healthy and relaxed aquatic environment