Synodontis decorus since 1980, Synodontis brichardi since 1980, Synodontis macrostoma since 1981, Polypterus palmas polli since 1981 -All are still alive. A Synodontis alberti died in 2003 which I'd had for 19 years.
Do Koi in a pond count? Like 18 years...they were my parents, though. I would feed them and watch them, if that counts. They got them when I was 6. They're still in the pond at the house I used to live in.
-Jon