Thanks for the interesting link Pat, as I always enjoy looking at those kind of statistics. However, I would think that major cities like Sydney and Melbourne (or even the other million-plus ones like Brisbane, Perth and Adelaide) would be able to support a worthwhile aquatic facility. Sydney Aquarium is decent but Melbourne's is fairly expensive for what it is, and yet both cities have over 4 million inhabitants. That does not even include the massive amount of tourists that visit Australia.
The real surprise is Germany, as with 500+ zoos (an astonishing number!) there still is no facility that rivals these American institutions: Shedd, Georgia, Monterey Bay, Baltimore, Tennesee or Aquarium of the Pacific. There are at least 20 major American aquariums that are top-class, but aquariums have never really caught on in the German land of zoos and I'm still waiting for the day when a truly great one is built in that nation. Many folks love the Berlin Aquarium, and with the two major zoos that city is competing with San Diego and Singapore for zoological paradise.