The work of the activated carbon filter is completed through the carbon bed. The activated carbon particles constituting the carbon bed have many micropores and huge specific surface area, and have strong physical adsorption capacity. The water passes through the carbon bed, and the organic pollutants in the water are effectively adsorbed by the active carbon. In addition, there are some oxygen containing tube energy groups on the amorphous part of the activated carbon surface, which enable the organic pollutants in the water passing through the carbon bed to be effectively adsorbed by the activated carbon. During the adsorption process, a layer of balanced surface concentration will be formed on the surface of the activated carbon particles. Under the effect of the surface concentration, organic impurities can be adsorbed into the activated carbon particles. Usually, the adsorption effect of the activated carbon filter is very good at the initial stage, but with the increase of time, the adsorption capacity will continue to weaken, and the adsorption effect will also decline. Generally, if the water quality in the aquarium is turbid and the organic content in the water is high, the activated carbon will lose its filtering function soon. Therefore, the activated carbon filter element should be frequently cleaned and replaced when using the activated carbon filter for water treatment.