http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7448.html
A lot of people who use what they call "living soil" have soil mites.
Those people claim they are beneficial and do not harm the plant.
I find them on and off and believe they either come from the worm castings or let themselves in.
Recently I started growing lettuce under T5s for personal use (I swear it's personal and for legitimate health reasons). Well this created a haven for gnats, and since I won't spray anything on my lettuce they are just going nuts. So I located an older mother plant who I knew had these soil mites living in the container, and took samples and spread them throughout my entire plant collection to see if they would keep the gnats down and possibly prevent aphids in the coming weeks.
Any thoughts on using these guys for pest control?