Kloud City &reg; Aquarium Fish Tank Biochemical Sponge Filter Cylinder Block, Suitable for Dia 4mm Water tubes This super biochemical sponge filter is a filter that keeps your aquarium always clean. The filter provides mechanical and biological filtration for easy, it use the air-driven system to create suction, that allows the sponge to capture floating particles in the water and return filtered water to the tank. To use : 1. Before use, soak the bio-foam in aquarium water for 5 mins. 2. During maintenance, always rinse the bio-foam with drained out aquarium water only. No tap water or hot water should be used at. 3. When re-using the bio-foam, do squeeze the foam in the water to remove all trapped air bubbles. This will keepthe filter stay submerged. 4. Suggest replacing the bio foam every 6 month, to ensure the filtering effect as well as the growth of the nitrifying bacteria. Material: Plastic, Sponge; Filter Color: Black; Tube Color: Clear Suitable for fish tank that capacity is no larger than 180L