Man that sucks, I have caused a few (more than I can count) floods in my time. I forget that I left the water on all the time.
Also, freshwater fish will not do well in straight ro/di water, there needs to be minerals and trace elements in it. Kent Marine & Sea Chem has products to add to ro/di water to make it fish safe. The fish at the typical local fish shop are in tap water, they might have a hard time adjusting to water that is very different than what they were kept / raised in. Might make your life easier just using tap water with a quality dechlorinator.
Joel