Hi and welcome to the forum
What are the tank dimensions (length x width x height)?
What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).
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All tetras do best in groups of at least 10 or more of their own kind.
Rainbowfish do best in groups of at least 6 and preferably 10 or more. Different species of rainbowfish that are similar sized, will hang out together.
Corydoras do best in groups of t least 6 and preferably 10 or more. Again you can mix a couple of species to make a group. eg 6 pandas and 6 julii.
Dwarf chain loaches and other Botia species do best in groups of at least 6 and preferably more. However, you need to add them all at the same time so they develop a pecking order. If you have a couple and add more late ron, the new ones usually get bashed.
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Unless the tank is really big, I don't recommend keeping Botias and Corydoras in the same tank. they don't always get along and the loaches might hassle the catfish.
Most rainbowfish do best in water with a pH above 7.0 and a GH above 200ppm. Most of the other fishes you have listed come from softer water with a GH below 100ppm and a pH below 7.0.