Thank you Rob and Martin for your comments.
How to get the shot?
Get to the aquarium early - so that you can get to the various tanks before all the little kids get there and start depositing their fingerprints, hand-prints, and nose-prints on the glass (to be fair, many adults deposit theirs as well). You have to shoot with no flash because of the reflection off the tank (a big white spot in your image kind of kills the mage), so this means you have to shoot high ISO - this was shot at ISO 1600 (1/160 second, f/2.8) - the Nautilus was shot at ISO 6400. Shooting close to the glass will reduce/eliminate any reflections from the room.
After you have done the shooting, you have the job of dealing with the high ISO noise in your post processing. I go through three stages of treating the noise with three different noise filters (the ACR noise filter in Bridge, PictureCode's Photo Ninja, and Topaz DeNoise), and then follow that up with a High Pass Filter (in Photoshop) to sharpen up the edges that get soften in the noise filtering process. Then I do my normal processing of levels, curves, cropping, output sharpening, etc.
Hope this helps. For those of you shooting film, this probably won't hep.