I have been using tap water(no treatment) for 6 months since I have had my chameleon. He is doing great so far! I suppose it depends on the condition of your water too and where you live. Many people use spring water bottled, or reverse osmosis. This is a great thing don't get me wrong but I am just giving you my scenerio also and telling you it is possible to not have to do anything to the water. When I bought him from the breeder, the care sheet mentioned nothing about special water. It is really a personal preference I think.