Very nice looking Oscar

The one inch per gallon rule works really well for small mass fish like neons or danios. But you have to figure adult body size and how messy a fish is. when buying fish we should only buy fish you have room for at the adult size.
Good for you for taking the Pacu back and sending the Tinfoils to your mom.

I hate to say it but your still way overstocked, hurry with the new tank

What kind are the plecos? If their commons they can get well over 12 inches. Plecos are also huge waste producers. Just some thoughts.
Carol