I once had some goldfish that had grown too big for the tank, the petshop wouldn't take them, but, he checked them for me to make sure they were in good health and told me how to introduce them to a pond if I could find one suitable.
Luckily, one of my friends had a koi carp pond and I put them in, it tooks hours to help them re-adjust and I'm glad I did it, when I looked at them last the were MASSIVE and had obviously thrived.
Just putting them in a pond is irresponsible, how do you know that they weren't ill and you have infected the whole pond with dropsy or whitespot?