Marina i25 is a compact yet powerful internal filter that easily clips onto the Marina goldfish aquarums or can fit any other goldfish or tropical tank that is up to 6.6 US Gallon (25 liters) with its secure suction cups. Since its motor is submerged in water, it is exceptionally quiet. The i25 comes complete with 1 Power Cartridge that is uniquely designed to enable the water to enter the center of the cartridge for an effective mechanical, chemical and biological filtration process. Upon entering the center, the water 1st enters the zeolite chamber so toxic ammonia gets removed, it then enters the 2nd chamber which contains the carbon so that polutants and odours get eliminated. The floating debris then gets trapped inside the cartridge, all to ensure your aquarium water is crytal clear. Cartridge change is fast and mess free.