I usually name mine something, not always nice names.
Jag Hybrid- Jag, my husband named him for me, I should have called him Destroyer. RIP, died last week.
Red Bay Snook- Predator, for the way it ate the feeder fish at the LFS.
Several Oscars- Red, Osc, Tiger, Jaws
Jack Dempsey- Jack
EBJD- Blue
Jaguar- Attitude
Betta- Sapphire
Many others over the years, have forgotten most of them.
Not very original names, but I cared about all of them, especially Jag, and Sapphire. I can only keep a betta in the office, but I wanted to have a fish everywhere I can. Can't sneak in a 55 or 75 in an office the size I work in.