South American Cichlids • 120x40x55cm (47x15x21inches) stocking idea

[Matteo]

Hi,
my name is Matteo, I'm from Italy.
I'm buying a new tank (120x40x55cm - 47x15x21inches) and I'd like to have some stocking idea. My tap water has these values: pH 8 kH 4dH, but I think I can use a bit of peat to have a ph around 7.

Do you have any suggest for the population of the tank?

I'm thinking about two solutions:
1. a group of Pterophyllum scalare: how many?
2. a group of Mikrogeophagus altispinosus + dither fish: how many?

If you have any other ideas, also for fish from Central America, please let me know it!

Thanks!
Matteo