The following mesmerizing video is of the "Kuroshio Sea," the second-largest aquarium tank in the world, at Okinawa, Japan's Churaumi Aquarium. The tank holds 1,981,290 gallons of water, and is large enough to accomodate multiple whale sharks, as well as 80 other species of fish and marine life:
Kuroshio Sea - 2nd largest aquarium tank in the world - (song is Please don't go by Barcelona) from Jon Rawlinson on Vimeo.
The window itself measures 8.2 meters by 22.5 meters, and is more than 60cm thick, constructed from seven acrylic-resin sheets (the glue formula holding the sheets together is a secret).
Which is all amazing, but begs the question....then what's the largest aquarium in the world? Apparently it's a title that's both highly sought-after and hotly-contested. Atlanta's Georgia Aquarium was the world's largest when it was built in 2005, with a tank that holds 6.3 million gallons of water and four whale sharks, but apparently when the Burj Dubai opens in Dubai, it will assume the title of world's largest aquarium (so claims the Burj Dubai and, apparently, Guinness).
But here's the thing...while it holds the dubiously obscure honor of holding the record for "World's Largest Acrylic Panel," it's tank only holds 10 million litres of water...that's about 2.6 million gallons, which would make the Georgia Aquarium's tank larger. So technically, the Burj Dubai's aquarium is the second largest, despite having the biggest acrylic panel. Nothing says "scandal" like some good old-fashioned aquarium judging shenanigans!
Anyway, even if they did have the biggest tank, it might be irrelevant given that the've been having a hard time keeping it populated.
On a side note, it's fascinating that the whale shark seems to be the standard gauge for measuring megaquariums.