I have a little info on soil mites. I recycle my super soil and grow water-only, so I've looked into this. A couple cycles ago with my recycled soil, when I opened up my batch from the aerobic phase of the recycle, it was teeming with soil mites. I was pretty freaked, so did some research.
It turns out there are thousands, maybe tens of thousands of species of mites. It's one of the biggest, most complicated family of organisms out there (the Acari). Very few of them are plant pests--just the ones that feed on live plant tissue. One of these fuckers is our familiar common enemy, the two-spotted (spider) mite.
On the other hand, soil mites feed on bacteria, fungi, protozoa, some on nematodes, and the decaying organic material in soil. They don't eat live plant leaves or roots. They are essential to healthy soil, like in a forest, and they are a basic part of the soil food web. There are many, many types of mites lumped together as "soil mites." A lot of them are microscopic. If your soil has a lot of organic matter in it, and the organic matter isn't sterile, it's probably going to have soil mites--it has to have them to do a good job breaking down the organic matter and making the nutrients available to plants.
I let my soil that was teeming with soil mites site for a few days and it settled down--like anything living that has a population explosion, the soil mites died off when they finished their job of eating up the anaerobic bacteria in the soil, and then their dead carcasses get eaten by bacteria and fungi and the rest. It settles down to a diverse, health soil web, and that's what you want if you want a living soil.
So don't freak out over soil mites. If your soil is crawling with them, just let it sit awhile, it will take care of itself. If you look at a healthy organic soil that has some age on it under a microscope, as I do, you will probably find some mites. It's ok.
On the other hand, if you see those two-spotted spider mites on your leaves, take em out right away. and come back in 3-5 days and spray again to get the eggs that probably hatched. And repeat and keep paying close attention. They are a completely different species and they suck. That's my .02 on mites...
