I wouldn't use NIX (a pesticide) directly on your snake. It has the same active ingredient in it that both black knight and provent a mite use and with both of those you take the reptile out of the tank and treat the tank.
Lots of people swear by using nix on their reptile and that it caused no ill effects that they immediately saw. how ever you don't always see problems with kidneys and other organs right away, it may be an accumulative effect or just stunt/enhance the growth of an organ.
Now there is a reason that both provent a mite and black knight are more potent. Both are an aerosol and are more of a vapour then a liquid that nix is and are better at penetrating the contents of the cage.