I always have to name everything (with the exception of my guppy fry---until they get old enough to distinguish themselves). I have a friend who has two male bettas and two females and she only named one. Only because he is a mean betta and tries to fight with EVERYTHING! His name is B*stard...isn't that nice? I don't really understand... since I refer to my fish by their names. I guess it's whatever floats their boats. Personality I think it's how attached to the fish the person is....I guess.