It's always a good thing to have one or two spare pumps just in case the
one you are using at the time goes out during the midnight hour when
stores are not open.

As for the pump that went out.... open it up and try fixing it. Mine go
out from time to time and they are usually easy to fix.

BTW also keep air stones in the pond running 24-7....that way you don't
have to worry about an overnight fish kill due to a non working pump.