Great post and research Jeff, thanks for answering my question. I would like to add a thing or two if i might about RO water that ive learned over the years.
Being that i am an aquarium fanatic, its well known that we test and retest our water and are always battling with things such as Ph and total hardness, kh etc etc. Ro water has become extremely popular in that end of the hobby for years now as a way to provide safe water for our aquatic friends. Chlorine is usually the biggest concern....and the most popular additive to city tap water....its also the one thats the worst as far as our fish are concerned so we use RO to decrease it. To my knowledge RO water is 99.9 percent effecient, and it makes the water what we call in the hobby as polished. Its true that it can bring the ph of the water down in scale to that of acidic water, but from my experience, if you have hard tap water, say on the ph scale of about 8.0 to 8.5 ( which is what most cities would be), after using Ro, it will only soften it to around 7.0-7.9. Now, 7.0 is considered neutral. Neutral means that it is a perfect balance between alkyline and acidic water. It still contains trace elements, it still has bacteria, its polished. Now keeping in mind that for every .1 of ph increase or decrease, the water has ten times the amount of elements in it, whether it be disolved salts or otherwise, for an RO filter to take the water all the way down the scale would be extremely hard. I agree with the fact that it does make it softer, ive seen it, ive measured it. But so far down the acidic scale that it has no trace elements anymore, i would agree. For that to happen it would have to be below a ph of 4.5....which is not to my knowledge found anywhere on earth. 4.5 occuring softly after the rainy season in the lower amazon river basins.
Now i do know that if it is matched perfectly to gallons per hour, that UV sterilizers will completely kill off everything in water....but thats usually just based on bacterial counts. Again, Uv will soften water, but it will not bring it down dangerously in the scale. RO has gained popularity as it will usually kill off bacteria which is good in an aquarium.....if its the right type. Killing all bacteria will cause havic which is why your not suppose to completely fill a tank with it...as some bacteria are needed for life and are considered good.
Okay so whats my point???? I thought you would ask. If you look at RO like i do, and this is strickly from an aquarists point of view, but ill try and adapt it to say your water bowl. I have a home RO unit, one commercially available and not one that would be considered a professional unit (which is probably what most ppl would buy and could afford). My tap water has a ph of 8.3, very hard. I have lots of disolved minerals, salts etc. I use the RO to purify my water for my water bowl. When i test the outcome of my RO, its now a ph of 7.0. It is neutral. It is now 1300 times less minerals, salts, and most importantly bacteria. It does however have the perfect balance of minerals and salts however. It also has the perfect balance of disolved acidic elements. So whats the difference. Its in a measurement called Kh. Kh is basically a measurement of the buffer ability of water...it is the ability of that water to stay the same. So i add it to my water bowl. It stays the same. I use tap water....it changes. The ability of water stability that RO creates is actually more useful in a larger sense. If you have used this bowl before, or if its new infact, sitting in the open air inside your enclosure will change the makeup of the water if you use regular tap water. Ro water will do the same, but it will take far longer, and will be a slighter increase then that of tap water. Tap water with all its glorious amounts of minerals when left to sit can actually become harder. As the water disolves into the air, the elements stay. You add more water, it brings the ph up and up and up. If you have an animal thats from any sort of rain forest, it will be drinking water it has never been exposed to. Hard water types almost never occur in rainforests...infact i can't think of one...please correct me if you can! Soft water, that of the 7.0 scale and less occurs often...infact 6.0 would be common. So what difference would this make to your animal if you provided it. To tell the truth with herps i could only guess. With aquatic animals its often the key to pandoras box when keeping, or more so breeding. For those of you who are familiar with Discus, they can be kept relatively long in hard normal tap water. However when breeding its almost impossible to hatch their eggs...why...cause hard water creates too much osmotic pressure which destroys the egg sacs. This is of course if they will even breed in hard water. Its also noted that animals of the aquatic type will also have way more brilliant colour when kept in their native waters, will live longer, and generally be more stress free...any general search on fish will provide tons of info to back this up.
So this leads me to yet another question, i just love water types so i have to ask. I know that alot of herps that are kept are from very wet humid conditions such as various rain forests. It also seems to me that alot of those are also hard to breed, or more so, those that are egg laying are often lacking in any real yeild as opposed to what they would be in nature. My question is, perhaps this is but one little misunderstood, or missed element in breeding and keeping. If you provide their native temps, humidity requirements, food, and light....and not their water, could it possibly be the missing link for some herps? The aquarium ppl know and understand this missing link, thus why so many animals are now being bred that couldnt be for decades. Maybe herps need the same boost? Now understanding that most commercial RO units will not remove everything, and that most beneficial elements will still remain in a small quantity...perhaps its actually useful. Just something to ponder for a moment or two. It just makes me wonder if all those amazon tribes and south american persons suffer from the ailments are described in your link? Just something to think about.
Sorry so darn long...i hope this makes sense but im sure several of you will be scratching your head!!! Thanks for reading, Shane.