It was Fasth's fourth NHL start and he has won them all. He has given up a total of four goals in those four starts.
The Ducks have won four in a row while Colorado has dropped back-to-back games.
Francois Beauchemin added a tally midway through the second period with Koivu assisting.
Semyon Varlamov allowed all three goals on 20 shots. Colorado has played 10 games this season and has been blanked in three of them.