Australia is hard to bring fish into. They check all luggage and freight coming in and if they find anything they fine you and destroy the livestock. We also have a list of prohibited fish (noxious species) and if you bring those in you get massive fines and possible prison time.
If you try to bring them in legally and they aren't on the noxious species list and they aren't on the importable fish list, they get destroyed. If they are on the importable list, they must go to a government approved quarantine facility for a month and that time can be extended if the fish die from something unusual. Whilst in quarantine, some species get taken to a lab for testing to make sure they are free of diseases. Any fish that dies during quarantine must be kept frozen and recorded (day it died, etc), then handed over to quarantine when the fish get released. After that the water in the quarantine tanks needs to be treated with high levels of chlorine before it can be disposed of. If you don't have a quarantine room you need to get a fish importer to quarantine them for you and there's a good chance their tanks will have Fish TB and various other diseases in. If you decide to build your own quarantine room for importing fish, it will cost you thousands each year just for the annual license.
