I had a male betta for 6 years and almost made it to 7, not many people can say that
but I do miss him, had an awesome personality that have not ever found again in another betta
Right now in my tank I have a glass cutter catfish that is my oldest, he is 14 years old he's been in 4 different tanks and 3 moves.
I have a Zebra tilapia cichlid that we've had for 7 years but he was already 6" when we got him.
A Midas that we've had for about 5 years and he was already about 8" When we bought him.
A four line catfish that we've had 9 years
An Asian upside down cat that we've had for 8 years and he was big when we got him as well. These are still alive living in my tank.
I have a pleco who's over 6 years now. Also had a Splendida Rainbowfish that lasted around 6 years. I have 3 rummy noses that are over 4 years now...guess that would be the tops!