Hi, welcome to the forum
I'm afraid fishtales is right about the tank. Member fcmf is our goldfish expert, she'll be able to help with them next time she logs in.
If it is a long time since you kept fish, you will find things have changed a lot. Our understanding of fish needs has developed and we now know they need much bigger tanks than we used to think. We now know of ways to set up a tank without harm to the fish. And we now know the importance of the water hardness when it comes to choosing fish.
25 litres is a very small tank, and is suitable only for a single betta (male or female) or shrimps. Neon tetras need a tank at least 60 cm x 30 cm. Zebra danios need a bigger tank than that - at least 100 cm long - because they are such fast swimmers.
But.....
If you could manage a bigger tank, even a 55 to 60 litre tank there would be much more choice. If you let us have some basic information such as water hardness and tank size (if you do get a bigger one) we can help you work out a sensible fish wish-list. I know that Australian laws prohibit the import and sale of some species which are easily available in other countries, but we can work round that if you like some of the prohibited species.
Please don't let what I have said discourage you. Even if you can only manage the 25litre tank, you could make that into an underwater garden with a betta or shrimps. Member Matt is our aquascaping expert and he will have plenty of suggestions along that line.
PS My betta's tank is an Aqua One, an Australian make