I've read about the type of mites that sit on top of the hissers, but I can see some tiny bugs (I assume mites) that just live in the substrate. I went pretty crazy cleaning to get rid of them and all it did was stress my colony. (fwiw, I have a small colony in a 10 gal tank so that's how I can see them). Do I need to worry about them? If you can imagine fruit flies without wings and 1/4 of the size (almost transparent grey, like pointed ovals), that's what they look like. They just crawl around the top of the substrate. I can see they have a few maturity stages, since they range quite a bit in size. I've noticed them flare up if the humidity is high or if the roaches don't like what I've fed them.