Considering you have to pay admission to City Museum ($12), (where the Aquarium is located) and a seperate Aquarium admission fee ($6) the Aquarium should be awesome and it is not. Your time would be better spent at one of St. Louis' other attractions such as the Zoo or Botanical Garden.
The World Aquarium is located within the City Museum (see separate review) in St. Louis, MO. I thought it warranted a separate review because you can only go to it if you have paid to get into the City Museum, but it costs an additional $6 per person. This aquarium takes up a portion of the 2nd floor of the museum. I personally didn't think it was worth the money. There are lots of animals to see, but there are way more at the St. Louis Zoo and the zoo is free! Enjoy the museum, but skip the aquarium.