While the Oregon Zoo in Portland does not have an aquarium per se, it does have a couple of fish exhibits.
Point Defiance Zoo: Aquarium (photo diary)
Museums 101: The Oregon Coast Aquarium (photo diary)
Columbus Zoo: Aquarium (photo diary)
Columbus Zoo: Aquarium reef (photo diary)
Oregon Zoo: Penguins (photo diary)
Zoo Boise (Photo Diary)
Oregon Coast Aquarium: Coastal Birds (Photo Diary)
Oregon Zoo: Otters (photo diary)