I LOVE ostentatious names for fish lol, I think it's brilliant. Very refined, very sophisticated. I've always said that if I got multiple fish I would give them very over-the-top names, but leave one of them very mundane. For example, I would introduce them as, "This is
Ignatius, and this here's
Ebenezer. We've got
Bartholomew, Amadeus...and this is
Steve."
Using your requirements, I would probably go with
Goliath Duoro
Ebenezer and call him "Weezer" as a nickname.
Goliath for the leader of the clan in Disney's animated 90's show Gargoyles. Betta fish have wing-like fins, yeah?
Duoro pays homage to my Portuguese roots, it's the name of a river in Portugal.
Ebenezer for
Christmas being my favorite time of year and the Dickens story living in my heart all year round.
It's not as fancy-shmancy as yours haha, but I like it.