Norton,
I went to the DC National Aquarium this past June when we moved here. I thought it was horrible. The displays are tiny and the animals have nowhere to get away from the seeing eyes. It has been show that animals in captivity do significantly better (less stress, longer lives, etc.) if they have hiding places. It also forces the tourists to spend more time at each display. All the displays were really dirty when I was there too. Overall I was quite disappointed.
Jenny