The internal filter filters water in small aquariums with a volume of 25 or 50 litres. This is taken care of by the large filter surface and the fine activated carbon sponge. The water flow rate is 120–240 l/h and can be adjusted with the water diffuser. The filter operates very quietly and saves energy. It can be installed standing up or lying down. The internal filter is sold as a complete set with a 1.5 m long power cable.