I love those exhale bags for convenience. But I've started doing my own fermenting buckets. 4 cups dissolved sugar in water added to half full 5-gallon black bucket of room temp water. Mix in a decent amount of baker's yeast throw on the lid toss in an inlet hose for a fish tank bubbler that I've hot glued to the bottom of the bucket and an outlet hose to push out the C02. Runs every other hour while the lights are on. I hit 900 to 1200 ppm on the co2 levels with 2 5-gallon buckets. I run the outlet hose to the circulating fan to disperse the Co2. They last about 2 weeks before having to redo the sugar mix. The only recurring cost is the sugar and yeast. You know when to replace the water once your tent stops smelling like a brewery.