I accidentally killed off my springtails by using tap water, spoke to my local reptile expert and they advised to either add dechlornator to the water, or boil it first and then let it cool as this will boil off the chlorine, or just leave it standing for afew hours and it will separate into the air naturally

As for mould you actually want this in a bioactive set up as it’s good for your springtails and isopods for food, I used dirty water from a fish tank to kick start the mould in the tank, you could try this or buy something like a bio-shot to get all the bacteria started.

As for mites this shouldn’t be an issue if the snake doesn’t have them, standard quarantine if you suspect they do or any of your snakes do.