There are
restrictions on what tropical fish can be imported into Australia. On the other hand, Australia has some outstanding native species, including some lovely pufferfish, so if you're prepared to make the effort to get in touch with
ANGFA, you can set about collecting and keeping some outstanding brackish and saltwater puffers most of us never get to see!
For the life of me, I can't understand why anyone in Australia would be doing anything other than keeping native fish. The range of fish species is astonishing. Do read Bruce Hansen's excellent chapter on Australian brackish water fishes in my book to get some ideas.
Cheers, Neale