I have two very large goldfish in a 100l with two plecs a lobster and a cuvier bichir. Because they are so big like everything else in my tank they get on fine with there tank mates. The pair are both 5 years old, the bigger one I kid you not his mouth is so large you could fit your thumb init. Great fish if you give them the right care and I would never think of them as just goldfish so much more to them than that.
My wife's goldie is about 9 years old now and 11" . She shares a 75g with a shubunkin. Awesome fish with a great personality. She started out all orange, but lost it all one year and is now completely white.
I currently have two: Naruto and Sasuke. They've been alive for almost a year now and a little under 2" each. They co-exist with my Apple Snail and seem pretty happy! They love picking at the plants, bubbles, and sometimes the Apple Snail but he's too big for them to even attempt to swallow! They've gotten used to the sound of my voice and what I look like that they automatically come over now!
I have a fancy fantail and a golden comet in with 8 tiger barbs 4 odesa barbs 4 ghost butterfly commons 4 golden pencil fish 2 common plecs 2 sucking loach and a pictus catfish all get along fine the pictus is only 2" at the mo but rules the tank.......
Its realy big and coloured amost red, what do you feed it? I have 2 common goldfishes and about 4 inches now, with me since last june. Its getting orange to red slowly. Feeding carrot, red pepper, sweet potato and green peas-all mixed in a mixer and add little spirulina salt vitamins butter gelatin. put it in micro for 8 mins. Gets fantastic colour