Removes and controls harmful ammonia. Immense surface area for beneficial bacteria to populate. Designed for use in the AquaClear power filter. Recommended for use in freshwater aquariums only. Available in a variety of sizes. Working double-time, the AquaClear Zeo Carb is a strong combination of activated carbon and ammonia remover. The activated carbon of this insert eliminates odors, discoloration, and impurities in freshwater aquariums. Reducing stress on your fish and maintaining a healthy environment, the ammonia remover prevents toxic buildup of ammonia and nitrite. About AquaClear Since 1978, AquaClear has led the market in clip-on aquarium filters with their consistent design quality. In fact, they invented the first ever hermetically-sealed clip-on pump in the late 1970s. AquaClear empowers fish hobbyists by allowing them to customize the filter media to fit their unique aquarium needs. AquaClear's longevity and success is no mistake with their adaptable products providing reliability and durability through the years. Size: For 40 - 70 Gallon Aquariums.