My 12" Goldfish that was given to me by a neighbour a couple of years after he'd one it from a fair! It came in a small bowl which it had out grown so was given a bigger one which it out grew again and then he had a 4ft tank all to himself!
He was called Jaws as he loved to eat and would grab your finger if you put it in the tank with him!
i had a barramundi(Australian native), and he out grew the tank (3 foot tank), but i guess that's what happens when you only feed him on gold fish. but he was a cool fish. i have a movie of him swimming around with a tetra stuck in his mouth..it's a little sick but i got over it pretty quickly.
My biggest fish is long fin zebra danio (female) which is about 1.5 inches haha..
But Our family used to have a koi with us (for 4 years+) He died last months... He was 16 inches long. Biggest among all koi inside the monster tank (180 gallons).
6 years ago there was even a monster koi(in my point of view) inside my family fish tank, (at that point I were studying and not really care about what my father brought home into our fish tank) "Potato" was 24 inches long
I have photo of the koi that just dead but didn't take any photo of Potato though (if somebody can tell me how to upload a photo in here, I would post hehe. I don't see the attachment box like I used to see)