I have had issues with mites in the past, but have found a few things that have almost cured the mite problem completely. (I dont think that you can ever be completely mite free) I found a mite spray that works well for me, it is called "Natural Chemestry reptile spray" if you need, I can try to get you a pic. I used OSB, ( a kind of plywood) I know that people use paper towels, but I tried it, and thought the osb works better, mainly because it is rigid, can be cut to the same size as your rack/shelving, but still absorbant. I sprayed the plywood until the surface was saturated (wouldnt do it in the frog room, it is a little nasty) then simply placed it on the rack with the cultures on top of it. I actually have 2 pieces. 1 for new cultures, and 1 for producing cultures that I am feeding out of. I also keep them on seperate shelves. since I have started using this, I havent noticed any mites in any of my cultures. I only spray the osb every 2 months or so, just to be sure. my cultures routinely last for 1.5-2 months (with no mites), they last until the media is completely gone. I dont usually use them that long, but they keep producing, and I keep them just in case I need them. If you want, pm me and I will tell you who I have found to have the best cultures imo.