oooh lucky, Melbourne is great for fish shops and the aquarium.
I doubt you'd be able to bring ADA soil back into the country though.
Here are a couple of places I've been that I thought were good:
http://www.facebook.com/pages/Subscape-Aquarium/165185040211176
This is the one bdspider mentioned:
http://www.facebook.com/upmarketaquariums