I would do something similar to HFF, they get people from all over coming to get stuff, wouldn't be as big as down here the demand and population is less, but have a wicket planted display tank that is well looked after, stock the general fish, i.e. tetras, corys, gouramis, cichlids, barbs, loachs, goldfish etc + a few others that probably wouldn't go fast, Arawana, senagalis, ghost knife elephant nose, maybe even a small marine section depending on demand. and set up systems with local breeders through FNZAS as well as importers, that way there will be mix's of fish.
Probably be in wellington, maybe just up from there.
Have a small reptile area, 4-6 tanks, including one display with water dragons, turtles and some capable fish.
also have a wall were customers can bring in pictures of their tank set ups to show + notice board for customers looking/sell for spacific items