There you go. An older specimen of a very slow growing fish is going to be larger, but not the norm.
Fish definitely grow to their tank size. I have some marble ctenopoma that my friend Jack gave me. He has some as well. Mine have been kept in various tanks over a year's time up to 210 gallons. His were kept in one of his 2600 gallon tanks. His are 3x the size of mine. There's some other fish he has that I also got from him at the same time and his are double the size of mine.
Fish definitely grow to their tank size. I have some marble ctenopoma that my friend Jack gave me. He has some as well. Mine have been kept in various tanks over a year's time up to 210 gallons. His were kept in one of his 2600 gallon tanks. His are 3x the size of mine. There's some other fish he has that I also got from him at the same time and his are double the size of mine.