The first aquarium I ever saw was the Monterrey Bay aquarium. Fascinating. I went in 1990. Later I went to the Tennessee aquarium which is also really good and then, when it was built, I had a 1 year pass to the Georgia Aquarium in Atlanta. I would take my kids and just sit and stare at the huge wall they have... The boys were 7 and 5, so after 30 minutes I'd reached the limit with their patience, but they enjoyed it too.
I loved to watch those grumpy old grouper slide by, and then to see the whale shark swim up and by the wall was amazing- those things are massive.
I was in Chicago once and had a plan to go to the aquarium there before I had to leave, but ended up in the Field Museum so long I never got over there.
That would be some good vacation planning- all the big aquariums around the country- hmmm.....