When and how should i get the C02 to my plants because my plants are still seedlings but they are close to the veggetive stage so when should i introduce the C02 and can i use any c02 because i dont have a fancy set up im using my closet and i have them in a hydroponics system that i made out of a bucket, net cups and an aqua air pump but can i just get c02 from paintball guns and use them or no? What should i do
You are going to have to worry about air circulation inside the closet and smell control way before you should even get as advanced as adding CO2. You can build adapters that can be run off of paintball co2 canisters, but you are going to need a different type of regulator to disperse the co2 evenly and in a timed fashion. It will be cheaper and easier to make sure you can get fresh air into the closet without the smell getting out as fresh air has plenty of co2 in it.
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http://www.ilovegrowingmarijuana.com/co2-level-marijuana/This will answer your questions>