Fluval Zeo-Carb is a premium blend of research grade Fluval Carbon and Fluval Ammonia Remover. Working together, these highly effective media eliminate liquefied impurities, odors and discoloration, while simultaneously removing toxic ammonia, for a clean, healthy aquarium. Combining two products into one frees up space inside the filter for other types of media. For Fluval filter models: 106, 206, 306, 406, FX5, 105, 205, 305, 405, 104, 204, 304, 404