Sounds sweet! I would either learn how to construct it with plexiglass (or glass) or do as mentioned and learn to waterproof the walls with just the viewing pains being glass. To make it easier on you I would also plumb it so that you can do water changes by pushing a button (much better than getting a ladder and vacuuming
Just an idea but if you wanted to make it really cool and natural looking then you could build a 3d background! It would look amazing!