Spring water, Filtered water, or distilled?

[SludgeMunkey]

Substrate generally doesn't matter unless you're keeping something like corydoras catfish that requires a sandy substrate. I all acknowledge that water requirements for amphibians is different then that of fish, but I felt that I should add that ro-di water does not adversely affect fish, if anything it is healthier than regular de-chlorinated tap water.

I should have been more clear pertaining to the fish and substrates. But, since this is a frog site, I'll focus on the issues of reverse osmosis treated water and deionized water. The issue is how amphibians regulate sodium and chloride ions internally.

Here is a recent article on the topic at Reptile Channel by Margaret A. Wissman, DVM, DABVP.

And thanks to Google Books, here is where I first read about it a while back, in The Ecology and Behavior of Amphibians.

Another good read that covers the topic is Manual of Exotic Pet Practice. Mark Mitchell and Thomas Tully. Elsevier Health Sciences, 2008. (This is a great book for anyone into herps!)