Hi, Did you know that Koi are some of the biggest goldfish and can easily weigh 20 lbs
Yes, and there a bunch of varieties recognized in Japan.
Read online that a Koi in England weighs 90lbs and is over 1.3meters or 4ft long!
And the whole reason they were domesticated was for food. Imagine how many people a 90 pound carp would feed.
That sounds like a tasty party. LOL. But to get that big takes lots of years. The koi are really a type of carp. The oldest known was over 260 years old!
I guess the reason we have so many carp, from goldfish, to food fish to big ornamental koi, is because they are so adaptable.
Yes, I'm thinking of getting a fish for my kids. 
They are so pretty. Even if you stick to regular goldfish, you can get lots of differnet colors and fin shapes--so much variety!