Okay it is not to cold for koi where you are, i live in illinois and worked for a watergardening place and it got -36 here last year, if it does ice over all you need to do is keep a hole open in the ice, koi are a type of carp and are very hardy fish that do better in cold water but do fine in warmer water as well.

That barrel AND your pond are fine for koi, their growth depends on a few things and area of the pond is one of them so the barrel might stunt the kois growth but it wont look weird and it doesnt need to be a 3 foot koi because it is safely in a barrel the only predators you should worry about is racoons. even a butterfly koi might do better since they are slower swimmers they would need less room. sorry to post twice.

Good to know. I am in central KS and am considering a pond.

it is not cold for koies but stıll ıts better to buy a heater

To update on my pond, based on the feedback here, I did add some koi to my pond. They have done well, except that they attracted a blue heron who enjoyed some of them. The remainder have done well, and the largest is now just over a foot in length.

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My grandparents had 3 koi in a hottub it froze for a few weeks and lived through with no probs lol