I do like the idea of using RO over distilled, always have. We also have to note that this is a study with humans and the warm blooded mineral and electrolite balance.
I think in areas that we find animals exposed to constant hard water, they'll be less able to adapt to not having this balance of minerals in their water. The water will have more of a stripping effect to the individual rather than replenishing. However, many people in hard water areas have problem with Kidney stones. Certain individuals cannot tolerate the high mineral load and it accumulates in the body.
I do think the Crytodactylus are going to benefit from increased supplimentation because of the likelihood that they are taking in a higher mineral level through their choice of insects in their diet. These guys aren't the ambush preditors that the felinus are, and are eating more of the mobile, chitonous insects. The elok aren't picky about what time of day they hunt either. I also find my elok have a tendency to prefer crickets over roaches. I'm also pretty sure that the felinus prefer softer body insects like roaches. We saw several soft bodied roach species while we were out as well as a few harder bodied species. It's very interesting to compare two different strategies of behavior from geckos that inhabit the same habitat niche.