Here is the best possible scenario for raising koi fry in Utah.

Have the largest possible pond with established water to raise them in. 90% of what they eat for a month or so won't be what you feed them, but what they find naturally as they constantly pick throughout the day. As soon as they hatch, they will live off their yoke sack for a few days and need no help from you until they are free swimming. When they are able to swim, their life goal is to eat and spend most of their existence thereafter doing just that. After they become about 3/4s of an inch long, they will begin to recognize you as a food source, and will begin showing up to eat when you're around, just like your grown up fish do.

Fry food is ground very small and even the smallest is large for new free swimmer. No worry, if you can find one with your naked eye, you'll see it picking at stuff you can't even see. Soon they will be big enough to eat that supplemental fry food you add and it is only a matter of weeks before you can start adding larger food. A good way to tell how large the food should be is to spend a little time watching them and observing just what size of food they are interested in. They usually won't bother with it if it's too big. Natural selection will thin out some of the weak, and some of the heartier fry will grow much faster. Some of these big ones will even eat the smaller ones. This is interesting, because as soon as your fry become free swimming, the adult koi will leave them alone. Not true with other fish like gambusia and goldfish, that will prey on your fry. These small fish will easily be swept into a skimmer, but are reluctant to swim in deep water, preferring to stay in the shallows or near the surface.

So keep your pump down low. It's hard to clean a pond without skimming up babies, but it's easy if you 'blow' the debris to the deeper areas, then skim it out. You will have poor results raising fry indoors, so avoid this approach. You'll need to start culling the less desirable ones when they reach an inch or so. What to cull for is up to you, and it would help if you're an expert, Japanese breeder. It takes a very well trained eye to guess what might be a nice Showa or a beautiful Kohaku someday, and you won't see the final result for quite a while.

I will say that I was going to cull some seemingly orange, plain fish one day, but on catching them and studying them closely, I could see some pattern emerging. I left them and a week later, I could visibly see they were starting to develop white they hadn't had before. Now one is promising four inch kohaku (which will still change, for better or worse).

But you must cull them, or you risk losing them all to overcrowding and eventual disease. Start by culling the obvious greenish, 'carpy' ones early. After that, if you aren't an expert, keep the few you really like that look promising. You'll eventually sell or give away most of them, but you just might get lucky and keep one or two treasures for your own. Surf around and you'll find some really great advice on culling. (see also 'Breeding Koi' and 'Koi Eggs')