At the MAPS conference here in Colorado a few weeks back there were some of the best growers in the United States. Surrounded by tons of psychedelic enthusiasts, the mycology booths were always crowded with people eager to learn more about this amazing fruit.
One topic has been brought up multiple times and was reconfirmed by my good friend Kyle over Blue Bear Mycology, and a couple other big players in the mushroom industry. Certain mushroom genetics do better growing in bags and others do better in tubs or large open air fruiting chambers.
SO, what are "bag fruiting" genetics? Well, to put it simply, it's the mushroom cultures that contain in their DNA favorable genetic phenotype that does well in a high CO2, low oxygen environment, which is what happens when you grow inside a bag or "in vitro". The only air that gets in the bag is passing through a small filter patch, which, if it's the smallest size allows for very very limited air and gas exchange. I wish I could show pictures, but due to recent legislation changes: "The change. A new state law with new requirements for psychedelic drugs, Senate Bill 23-290, goes into effect July 1. It will ban not just paid advertising but all forms of advertisement for unlicensed guides who are offering mushrooms, among other restrictions" I am unable to do so.
So take from this:
When sourcing genetics, ASK how the mushrooms have grown out and what techniques were used.
Do your own tests by growing out the genetics in multiple different grow styles.
Once you've figured out what genetics you like best and do best in your conditions, save those genetics and continue to use them!
Mushroom cells respire by taking in oxygen and releasing CO2. As the spawn colonizes the substrate in the bag it will become CO2 dense. The smaller the filter patch size (.22 micron being the smallest), Some mushrooms do better growing this way where you don't have to modify or cut open the bag at all to get huge fruits. Usually however, after a good "pin set" is formed, cutting off the top or cutting a slit in the bag gives more fresh air exchange which is the standard way if you don't know your genetics that well yet.
Of course there are plenty of other ways to grow mushrooms. Large tubs, small tubs, buckets, bag side/top fruiting, and many other ways people are getting creative with. Personally, I like the ease of bags and have an impulse sealer so I can easily drop spawn into a bag, reseal it in front of a flow hood or still-air-box, mix it up good and then just play the waiting game!