Every bag I've used has always been filled with life (soil mites, spring tails, etc). Not just a subtle population either, I'm talking an abundance of life in each bag.
I use the bags for my quick pheno hunts in 3 Gallon Grassroot Fabric Pots and surprisingly, things work very well. Due to the limited rootzone and soil amount in each pot, it's crucial that I stay on top of top dressing, even with short veg cycles. The last thing you want to do is have your plant run out of food, and when you use slow release amendments, it's almost impossible to catch back up without having to supplement a water soluble into your rotation, so persistence and consistency is key - for those of you reading this that want to do smaller pots like me. Always, always, always stay on top of top dressing!! But, if you're running a larger - or substantial amount of soil volume, top dressing might not be necessary because as you know, each bag is technically designed to last an entire run with just water. But, the main caveat is how much soil you use and how long you veg will dictate just how much nutrients they use up.
Also, use a BTI with each bag to prevent any fungus gnat infestations. I usually prep each bag a month in advance by using the BTI frequently at first until I for sure notice 0 gnats. I also begin to top dress each 3 gallon pot with craft blend, BAF, Cowoco castings & kashi gold to kick start that biology. Though the top dressing is not essential if you're large volume, once you get…