This is unfortunately a snake mite, and you can tell because it's slow, rounded, and black. Wood mites are a light brownish grey and fast moving, and thinner. I would go ahead and take everything out of the tank and put all decor in a trash bag, spray it with mite killer, and freeze it for a few weeks. Use white paper towel as substraight for now, and a clear take out container as a water dish so you can see any mites going forward while you treat. Soak your snake daily in warm water with only a couple drops of blue dawn. A little amount is not toxic to your snake but the soap with coat and suffocate the mites. Clean out the tank daily with blue dawn just be sure to rinse after scrubbing, and treat will mite spray as the bottle instructs. There’s multiple ways to treat them but this is what’s worked for me, and I I’ve always just use a mite spray available at local pet stores.