Nation 90-year-old fish named Methuselah believed to be the world’s oldest living aquarium fish January 27, 2022 Asha C. Gilbert, USA TODAY Comments Off on 90-year-old fish named Methuselah believed to be the world’s oldest living aquarium fish Methuselah, an Australian lungfish, is believed to be the world's oldest living aquarium fish at 90 years old.