Many zoos, museums, etc. use RO water as it prevents excessive calcium build up on exhibit viewing windows (making cleaning a real chore). We, too, use it for the same purposes more regularly, however, we (the wildlife center I am curator of) have been using good old fashioned tap water (aged) for over 20 years and have never had a single problem that we are aware of. The water quality in our town is excellent so additional filtration devices aren't necessary at this time. I believe there are certain trace minerals that may get filtered out in other systems that normal tap water allows; but that is just me. At my home, on the other hand, where I breed and maintain most of my indigos, I use water that has been filtered by a system called the "Wellness Filter"; one of the best water filtering devices you will ever find. Our community doesn't exactly have the highest quality water so I installed this table top filtration system (kind of like a mini water treatment plant). The initial investment was around $900, however, it has a lifespan of over 30 years w/no hassle of filter replacements, etc. It is easily cleaned by backwashing once a week. Just something to look into. All of my indigos have done exceptionally well with this water source and I haven't lost a single one due to the hydration problems that have been discussed.
If there is one thing that we can all agree on is the importance of providing fresh water daily for these animals (in fact, all of my other reptiles get the same frequency of water changes whether it is my gila monsters, various boas/pythons, crotalids, various arboreal vipers, etc.). Hydration is certainly one of the most important elements for long term success.
Rob Carmichael, Curator
The Wildlife Discovery Center at Elawa Farm
Lake Forest, IL