"a good medium" is a correct and usable phrase in written English.
For example, "The best way to mediate the issue was to find a good medium between the two sides."
Was the theatre a good medium for this message?
IS MONEY a good medium to spread messages?
"This is a good medium to do it in because it's a very low-stakes medium".
Governments realised I was a good medium for getting that message across".
Writing is a good medium because the tears don't get in the way.
Of course, there is the question of whether phones are a good medium for pornography.
Theater turns out to be a good medium for probing the scientific controversies as well.
"Fashion is a good medium to get people to understand that furniture is more than a prop," Mr. Moss said.
But surviving in pounding surf is difficult, and sand is generally not a good medium for biologic preservation.
Why is the tea and design workshop a good medium of communication for mothers and daughters about fashion?
"It's a good medium, a good audience and they're captive to some extent," said Dominic Stead, the chief executive of Inviseo.
