in the newbie area are many recent posts (a lot by yours truly) about c02 mixes. I am using 2 coke bottles with 5 cups sugar filled with water and 6 packets of " active dry yeast" purchased at my local shopping market for $5, stir and they keep (in a 3x4x8 grow room) for about 3-4 weeks until the bubbles stop and I have to replace it. i have 19 plants just 6 days into flowering, they love it! smells like warm beer. M-m-m-m! beer and pot what could be better?