1. Fine - Hole Anti - leakage Structure: The specially designed fine - hole mesh bag can effectively prevent the leakage of small filter materials such as protein cotton and activated carbon, ensuring that the filter materials can play their roles without scattering in the fish tank and affecting the clarity of the water quality. 2. Compatible with a Variety of Filter Media: Whether it is protein cotton to remove yellow water or activated carbon to adsorb odors and impurities, this mesh bag can well accommodate and give full play to their functions, suitable for various common aquarium filtration needs. 3. Available in Different Sizes: Different - sized zipper mesh bags are provided. You can choose according to the size of the fish tank, the space of the filter, and the amount of filter materials required, meeting diverse usage scenarios.