Slim Filter Cartridge Bio Carb with Ceramitex BEST FOR TROPICAL FISH&gt; Slim Filter for Tropical Fish with Carbon Ceramitek MARINA SLIM FILTER BIO-CARB&gt; is a Genuine Replacement Cartridge for All Three Marina Slim Filter Models (S10, S15, S20) ACTIVATED CARBON&gt; Effectively Removes Pollutants and Odours CERAMITEK&gt; Highly Porous Ceramic Biological Filter Medium, Optimizes Biological Filtration EASY TO USE&gt; Disposable Cartridge Should be Replaced Every Two Weeks for BEST RESULTS!!