Pffft, that only the 2nd largest...
WOW, very impressive. They got Whale Sharks in there, WOW, that's big. In Hawaii I had a 150 gallon salt water tank. It takes a lot of work to reach a near self sustaining level of cleanliness, filter, temperature, salinity. The local Waikiki Aquarium, really nice with cutting edge research, pumps ocean water directly from ocean to the tanks and back to the ocean to provide a stable environment. They use some filters, pumps, etc. but primarily rely on the natural ocean water itself.