Wont get much co2 from them bags either, you need 20pound tanks and regulator, and controller to release when neededI'm going to echo what every one else is saying here. I'd advise getting your VPD dialed in foe a few runs before you go with Co2. If you aren't in a sealed room, meaning your are exhausting out of your tent, you are going to be exhausting that added CO2 as well. A sealed room is ideal in those circumstances. You do also want to run the room hotter with CO2 because the CO2 causes the stomata to close on the plant and the extra heat is needed to induce them to transpire (sweat) and take up water / nutrients from the root zone.