what fresh water fish can grow large in a pond?

Koi carp seems to be the biggest. I have found a site where the biggest goldfish was carried by a fisherman in the rivers of France. Although many people believe that this fish is really true. But some are so very skeptic. In a certain study, koi carp may weigh up to 90lbs. That's really huge. You may read the full story here about the biggest goldfish found in France: http://newsflavor.com/world/usa-canada/biggest-gold-fish-found-in-france/

Koi and goldfish are both ideal for ponds, Koi become larger then goldfish but both are hardy fish. Though both descend from Carps they are totally different species, it is possible to have both in the same pond and it has happened that they cross-breed and produce offspring which are sterile. Both are ideal pond fish, certain plecos grow large and being part of the catfish family some can adapt easily to a pond, though I once read somewhere that they are territorial. Another consideration when choosing what fish to have and how many, is the size of the pond, weather conditions (the colder the area you live in the larger/deeper the pond must be) and other water conditions.

All of the ones you mentioned will grow very large in a pond. I would recommend common goldfish- the ones sold as feeders. Fancy goldfish do poorly in ponds because they are more delicate, and they don't grow as big. Plecos can get over a foot, I would recommend them too. Koi grow large but are very expensive, though they are beautiful. Goldfish are good because they are very hardy and very cheap. You can get feeder goldfish in the United States for 13 cents each, ten for a dollar. These fish are tough and can get two feet long in a pond. They also come in many colors and combination, mostly of gold and white. They probably grow the biggest of all three, are the hardiest, and most of the time the cheapest.