What you are describing are wood mites. These are harmless to the animals, and more just a nuissance to the keeper

They are very common in naturalistic vivaria. If you wish to get rid of them you will need to clean out your tank completley and bake just about everything, (the plants can be sprayed with a weak solution of water and dishsoap daily for one week, then rinsed thoroughly), and be sure that anything new is sterilized before it is added to the tank. Of course, no harm will be done if you just leave them be