I have seen many videos with koi that are 3 feet (around 90 cm) long. However, I also know that some koi from desired varieties are really expensive. If I am buying koi from Petco and Petsmart, does it have just as much likelihood of growing to become 3 feet long? Or do I have to buy specific kinds of koi, from particular breeding stock, to have the koi reach such a size?
I have never seen Koi advertised as any large type, although there are likely some genetic differences. In 25 years I have bought several Koi and raised a couple spawns. The adults have been 24 to about 32 " long in the same pond . My pond is only about 5 ft. X 10 ft. I have seen many home ponds , occasionally fish up tp 3 ft , they have always been in very large ponds. Also ,no pond owner has ever said they purchased large strains of fish. Also talked with a professional breeder ( he went to Japan to select breeding stock) and he never mentioned larger types. So , many Koi , but not all , will get to 3 ft , in a very large pond.