I have had issues with mites. In some containers. I find composting the substrate longer makes a significant impact though. Thoroughly mixing. With larvae I think it's important for their development. Future horns, black spots, blah blah blah. Dog food, other larvae, I suppose could be adequate substitutes. The Japanese rhinoceros I'm keeping are pushing 45g. Anything proven... Not a thing. Some companies in Japan ferment 3x, supposedly. I have yet to try it with the stags.