I have been keeping Arowanas for ages. since in philippines, i have had asian arowanas, silvers also.
In nz, as far as i know, i have seen australian, silver, black and asian.
there is one asian for sale now at a site that we do not speak of, its $4000! but its the best you can get pretty much. its 2500 in singapore.
the Australian Arowana that livingart is selling is a nice one, i have one, They are aggressive, they dont need a HUGe tank, and really cool fish, you can Actually enhance their colour with some nice lighting, although limited enhancement, butlooks nice.
Always keep in mind, arowana eat alot! they poo alot and digest food rapidly, filtration is a key thing here. massive filtration is important. Regular water changes.