In the meanwhile I found a compressor company nearby.
Can you help me to choose the right pump for my rectangular shaped pond 100'x450', flat bottom, 8' deep?
Here you can see all the oilless pumps with specs:
https://www.dvp.it/en/customer/dry-vacuum-technology.html
Starting from the right compressor maybe I can calculate specs for all other necessary stuff.

I think I need at least 2 air station per 2 9" membrane diffusers each running 7 or 8 hours/day to circulate all the water. Is it correct?
If it is then I need a pump at least 4 CFM at 7 psi, right?

Thank you and have a good sunday

Filippo