I am using an old Beer Fermntation container. It releases constantly so the Co2 that is released when lights are off is wasted. It is cheap though. I flower 2 plants at a time and it works well for me. I start with de-chlorinated water and add activated dry yeast and sugar. In my case, because of the large container, I add 8 cups of granulated sugar and 8 teaspoons of yeast. Within 24 hours you are making Co2. You have to monitor the activity and add more sugar and yeast as needed. I ran a hose from the top of the fermenter to pop up inside the scrog about 2 inches above the plants. Co2 is heavier than air and falls down into the canopy. I have attached a couple photos. I also keep the fermenter covered with a towel to keep the light out. The yeast like it dark. The clear plastic thing on the top of the fermenter is a fermentation lock which allows excess Co2 out and keeps mold and other invasive creepy crawlies out of the fermentation tank.