As long as you follow the instructions on the dechlorinator then you wont be able to poison your snake with it, the stuff dissipates very quickly in the water anyway. A few drops per gallon is all you need to use, and hell it sure couldnt hurt the snake to drink less chlorine, which is the same stuff you put in your pool and the same stuff they gassed the trenches with in WWI (Mustard Gas). Chlorine can be really caustic stuff, chlorine is the same stuff as bleach, bleach=chlorine. On the other hand, if you dont have chlorine in your snake water, bacteria will grow that much faster in it, especially in a nice and warm snake tank. That said I dont think there is that big a difference between using chlorinated water or not, however I personally just use reverse osmosis filtered water for my snakes, I get it down at the water store on the corner, this is the same stuff I drink, if I wont drink tap why should the snakes that I love have to?