Don't even get me started on my mite problem! I have these mites that are 2-3 times larger than grain mites, hard shelled, and quite fast. Grain mites do not do well in dry containers, but these mites breed best in dry containers, and most of my bugs are darkling beetles, which I keep on the dry side. Plus, these things spread to other cages like wildfire. However, I am currently breeding a variety of springtails, and I am introducing them to recently sterilized cages to prevent mites from re-infesting them. These mites came from potting soil, which I had been using in place of coco fiber a few months back. Bug keepers be warned, do NOT use potting soil, or you might have a really bad mite problem very soon....