I am also looking to prevent water marks....I am going to be trying out Ryan's idea of vinegar (thanks! thats great idea!) and also trying distilled water, and also Dasani/or reverse osmosis water which was recommended to me by a few chondro keepers who use acrylic caging.
Is distilled water the same as reverse osmosis?
Is there any problem with snakes drinking distilled water as the only water source or should regular tap water also be provided as distilled water has no minerals?