Biochemical filter: Made of ultra-dense thick cotton, with good water absorption and high permeability, which can effectively filter and decompose dirt. Thick filter cotton: Hard and soft cotton to the touch, can be washed repeatedly, durable. Aquarium filter pad: It can be cut into any size according to your needs, easy to use. Aquarium filter cotton: Suitable for seawater, freshwater, aquatic plant tanks, wide applications. Aquarium filter: It has powerful filtration ability and can be reused after cleaning.