Growstone GPGC33CF Gnat Nix 9-liter bag is an earth friendly, 97 percent recycled glass product. Gnat Nix controls gnats at different points of their lifecycle, therefore preventing adult emergence from hatching larvae and deterring females from laying eggs in the growing media. As a result, their lifecycle is interrupted, and its population significantly reduced. All you need to do is apply approximately 1/2 - 3/4-inch thick layer of Gnat Nix top dressing to fully cover the surface of the growing medium in your growing containers. Make sure the entire top surfaces of all your growing containers are fully covered at all times. Irrigate gently to avoid disturbing the protective physical barrier of Gnat Nix.