AquaClear Ammonia Remover is ideal for new or heavily populated freshwater aquariums. It removes and controls harmful ammonia and nitrite, creating a healthy aquatic environment. Controlling ammonia levels is critical for reducing stress on fish. Available in the following sizes: Filter Insert for AquaClear 20 single or 3 pack Filter Insert for AquaClear 30 single or 3 pack Filter Insert for AquaClear 50 single or 3 pack Filter Insert for AquaClear 70 single or 3 pack Filter Insert for AquaClear 110 single