Great points made on the 24/7. Always learning here on FFHe doesn't focus strictly on Pacman Frogs. They spend 24 hours a day 7 days a week burrowed in the substrate. If it is saturated with pure water then it steals their vitamins and minerals. It is no different than using that water for their soaking dish which is not to be done. So if its not ok to use that kind of water for saoking then why in turn would it be safe to use for the substrate too? The frog will lose valuable salts, electrolytes, and minerals, become ill and die. There are far more experienced breeders that can back that up. Philippe de Vosjoli would be one of those breeders. In the world of Horned Frogs he is who most look to for how to house their Pacman's. There is a lot of conflicting info out there and so many disagree with their care, but some things have to be learned the hard way like not dechlorinating bottled water and assuming that it does not contain chlorine.
John has a good thread somewhere here on the forum that compares the various water type available. These are not tree frogs that pend their time up off the ground. The stayed burrowed for days and the constant exposure to that kind of water is fatal. This happenes over a long period of time, but eventually the frog succumbs to the imbalances in its system. Many become bloated once they get sick.
I'm not trying to start a conflict, but I can assure you that it is not ok for these frogs. Distilled and R/O are both pure water with nothing in it unless minerals and salts are added. It will literally leach the life from them.
Here is John's post. http://www.frogforum.net/vivarium-te...hing-else.html