Silver is AED 199 and includes the Aquarium Tunnel, the Underwater Zoo and Penguin Cove. Gold, AED 269, adds a glass boat tour, fish feeding and discounts on animal encounters; Platinum, AED 399, adds skip-the-line access and a complimentary animal encounter. The aquarium's own page gives its hours as Monday to Friday 11:00 to 21:00 and Saturday and Sunday 10:00 to 21:00, with last entry at 20:15; the mall's page for it says 10:00 to 22:00 every day, so check the day you go.
The aquarium's own site also sells it with At the Top, Burj Khalifa. At the booking step, where the fare categories are named, an adult (8+ years) pays AED 319, or AED 349 in the slots starting 16:30 to 19:00, and a child aged 3 to 8 pays AED 279; the AED 279 on the tickets page is that child fare, not the adult one. Our combo ticket is on the card above.