Beautiful Koi you guys have :) I'd love a Koi Pond someday..but I'd be afraid of the upkeep :P Since I live in Ohio, they'd get cold pretty quick in the winter. How do you guys do water changes on those? Is it hard to keep the water clear and smelling like water rather than a swamp? My Grandma and Grandpa had a pond with a ton of Goldfish, it was green and smelled horribly :P
Some people do water changes on a pond, some don't. You will have to make water changes if it is overstocked. However, if it isn't, large enough and planted enough you won't have to. I never do. But I do have an overflow outlet for when it rains. So I guess every time it rains my pond gets a water change. My pond has never smelled bad or anything. My guess that the reason your grandparent's pond smelled bad was due to a lack of water movement. Stagnate water always smells.
The deal with having a pond and being up north is that you have to know the depth to which your ground freezes and then dig the pond 1-2 feet deeper. This will enable you to overwinter the fish in the pond. Still, when you do want to build your pond, find someone in the area who specializes in ponds. Trust me, it was the best decision I ever made with my pond.
Have any of you guys browsed koi auction sites? They have beautiful fish, but they're sooo expensive. I've seen koi selling for over $2,000!!!
Also, would you rather buy a small koi and watch it grow or buy a large koi? I'm in a conundrum. All of my koi are 12 inches and larger. Koi of those size are $100+. As much as I love them, I can't afford to drop that much on a koi. But I'm worried that my larger koi would bully a small guy. Or that the small guy would be too shy to come out and starve to death (that happened to me before). Another option I have is just to not introduce anything new since I have a good thing going.