Regarding Mr. Kiel's response to you, he's not contradicting anything that I read in that other thread I linked to. The water they sell, they do indeed use for all their exhibits. They use the same exact water for their cold-water exhibits since they're basically exhibiting things that can be found right outside their door.
However, they do not use that water "as is" for their "exotic" displays... which are more or less what we all have for aquariums. For their exotic displays, they start with the water they sell, then run it through another set of particulate and sand filters, carbon, ozone, another UV
filter, and finally a protein skimmer, before they even use it.