Biochemical Filtration: This aquarium filter has a box containing biochemical cotton that collects and filters waste from the water, creating waves and a circular flow that promotes the growth of beneficial bacteria, creating a healthy water environment for your fish and turtles. The biochemical cotton is washable and reusable. Increases Oxygenation: The air intake on the aquarium filter increases the oxygen level in the filtered water, making the fish more active. In addition, good oxygen supply helps the growth of beneficial bacteria such as nitrifying bacteria. You can adjust the oxygen supply by turning the air intake valve. Note: The oxygen intake valve should be placed outside the aquarium and in contact with the air. Ultra-Quiet: The high-quality pump motor operates quietly. It produces only 35 dB, almost like a whisper or the sound in a quiet library. We recommend turning off the rotary knob and stopping the air intake process at night to reduce noise from the filter pump. This does not affect the function of the filtration system. Easy to Clean: It is very convenient to remove the biochemical cotton and wash it, or replace it with another filter media. If you have any questions about our products, please do not hesitate to contact us.