"Slim Filter Bio-Clear replacement cartridge fits all 3 Slim Filter Models.
Ideal for goldfish, it combines zeolite and Ceramitek in 1 cartridge for a
healthy aquarium. The zeolite effectively adsorbs toxic ammonia and reduces
stress on fish, while the Ceramitek, a highly porous ceramic biological filter
medium optimizes biological filtration. The easy to use disposable cartridge
should be replaced every two weeks. Never replace all filter cartridges at the
same time in order to ensure constant presence of beneficial bacteria."