AquaClear Nylon Bags are fine mesh filter media bags. AquaClear Nylon Bags make media maintenance even simpler. Made of fine mesh, each bag is designed to hold small-grained filter media and allows excellent water penetration. The bags can be used in fresh or saltwater aquariums. AquaClear creates a wide variety of products for freshwater tanks such as fish tank accessories, fish tank decorations, and aquarium filter media that is perfect for large and small fish tanks.