C02 - Best Natural Source?

Brewers yeast, sugar, and water.

Check out Amazon they have CO2 for grow tents IDK if they work though

On the subject of Reishi liquid culture, there are quite a few websites out the that sell them. Mycotown.com, Gourmetmushrooms.co.uk, mayamushrooms.co.uk. Which one is best I don't know but seem to be the most reputable I've found. Reishi need it very warm and humid, not something you want in your tent but you could direct the airflow to your tent inlet, lots of co2 there.... Hope this helps

Hi mate, I'm in a 2x2 cabinet and can't find anything for that space. All are for larger spaces. I'm not entirely sure if this works but I use bicarbonate of soda and vinegar. put a small amount in a jar and sit it behind my circulating fan...It releases co2 but how much I don't know. Hope this helps and good luck

Take a bottle cover in foil add cup of white sugar room temp tap water and some brewers yeast. Or... Up ur air flow sleep where ur tent is and run ur lights at night and OMG we as humans can pump out some co2.. Blurple lights kill.shrooms in my experience go with white lights and shrooms produce co2 only when they fruit otherwise theyUSE THE CO2

I have 4 large dogs that come to our bedroom to sleep at night great free source.