In time of fire, most importantly, you should save your own lives first.
Next, if you have time, save your valuables like money, jewelleries, important document (deeds, certificates), etc.
Next, if you still have time, you can try to save your fish by packing them in plastic bags, pails, ice box, etc...
But if you can't bring them with you, probably you can bring them outside the house (in pails or glass tanks), and put them in an open space/place far away from buildings, trees or things that can burn.
Glass is a good insulation but it must not get heated up, else the fish will also die when the tank water get heated up.
Switch off your house main circuit breaker if possible to prevent electrical fire which are very dangerous.
These are the only things that I can think of based on my limited knowledge.
Here is a good article on what to do during bush fire:
Up to date information about bushfires, storms, flooding and other emergencies from around Australia, along with advice to protect you and your property.
www.abc.net.au
But for best advice, consult your local fire brigade on what to do.