those mites dont eat dirt, they eat plants, especially ones that may be ill. my rooms have dirt all over the floors, dried leaves in the corner sometimes, lawn mowers, tractors, weedwhackers, used soil, new soil, dogs, chickens bathing in new soil....right on the other side of the grow room entrance, in a dirt floor barn.......yet....no mites in 10 years(ever) but clean is good.
mites come from buddies, their clones, and their visits.