I have a 12 gallon tank set to 25 degrees Celsius. I am wondering what fish to put in it. I don't want all small fish. And would like to know how many of the species you've chosen. And it is sand with article plants.
With a 12 gallon you will not have many options for large fish.
Have you cycled the tank? What is the pH of your water? You need to select fish based on your water hardness. You can normally pull that up from your cities water reports found online.