Who are the characters in the book the fourteenth goldfish?

In "The Fourteenth Goldfish" by Jennifer L. Holm, the main characters include Ellie, a middle school girl navigating the challenges of adolescence, and her grandfather, Melvin, a scientist who discovers a way to reverse aging. Other significant characters include Ellie's mother, who struggles with her father's unconventional behavior, and her friend, who provides support throughout Ellie's journey. The story explores themes of family, science, and growing up.