[【Double Filtration】This biochemical cotton inside the filter can collect and filter the waste in water create a healthy water environment for your fishes. The biochemical cotton is washable and reusable. The U-V lamp provides secondary filtration turns the green water super clear. (PS When the U-V light is on a small amount of internal light can be seen through the cutout at the bottom of the filter.) 【Timer for U-V Light】A timer which controls the U-V lamp to turn on at the options of every 4 hours 8 hours 12 hours or 24 hours provides you great convenience as it is not necessary to have the lamp on all the time. PS: The timer can only control the U-V lamp not the water pump. 【Two Ways of Use】 AERATING MODE -The air inlet on the aquarium filter will increase oxygen level of the filtered water make the fish more active. You can adjust the oxygen supply by spinning the valve of air inlet. 2. RAINFALL MODE- Filtered water goes to the spray bar and flow out from the holes back to the aquariums to create water agitation at the surface which is very favorable to fish. 【Ultra Quiet】Using Dimension: 6’’(L) x 2.5’’(W) x 13.8’’(H). Premium pump motor is noiseless during operation. We recommend to turn off the spin button and stop the air inlet process at night so that the filter pump will be more quiet. This way it will not affect the operation of the filtration. 【Easy to Clean】It is very convenient to take out the biochemical cotton and wash it or your can replace with a new filtered cotton.]