Features: 1.Imitate plant fiber, less resistance to water, strong water permeability, effective filter dirty, let clean water penetrate to the bottom. 2.Moderate pore density fiber can effectively decompose impurities in water, reduce fish mortality and protect water quality. 3.High density, moderate thickness, effective secondary filtration of residual water, suspended matter impurities, sediment and other large particles, nitrifying bacteria can effectively decompose impurities in the water, purify tank water quality. 4.It can be used for upper filter, built-in filter, waterfall filter, freshwater, salt water and other equipment. 5.Using hollow polyester fiber quality, soft, strong water filtration, cleaning and can be repeatedly use. Specification: Item Type: Aquarium Filter Cotton Material: cotton Color: white, black, blue (optional) Size: approx. 100x14cm/39.4x5.5inch Product principle: biochemical filter cotton is a kind of filter material widely used in aquarium, which is suitable for Marine tank, freshwater tank, aquatic tank and other ornamental aquarium, mainly improving water quality and improving fish survival rate. It is a filter material with both physical and biochemical filtration effects PackageList: 1 x Aquarium Filter Cotton