As a rule of thumb, Koi don't jump. Usually only if something is wrong with the water or with them.
Have you checked your water?

the water levels are ammonia 0.25, pH 7.0, nitrite 0.25, do I need to do any other water tests?
the salt test revealed that we are low on salt and I will be adding that later this afternoon. Could this be a contributing factor? We have 11 koi in our approximately 5000 gallon pond and they are getting very big fish. Is this also part of the problem?

Koi do jump and not always because something is wrong. I assume that this is a new pond with the readings you are getting. The readings are higher than I would like but shouldn't be that much problem. I seen a lot of koi that will jump for no other reason than to get your attention so that they will get fed.
Mike

Thanks Mike. Actually our pond has been around for a while. We bought our house two years ago and the pond came with it. The koi are probably close to 10 years old from what our neighbors tell us. They are getting very big with our largest probably 30-36", a majority about 20-24" and the smallest close to 16". We haven't had many problems, but we've never really done water readings either. Should I add salt and/or a water treatment or just recheck the readings tomorrow and see if the levels are still the same?

I would keep an eye on that. Jumping is usually indicative of a water problem. pH, Amonia, nitrate levels. All or either. This is particularly true if they start jumping, and weren't jumping before. If you've added new fish, plants, or made any changes or done any maintenance such as water change. You are going in the right direction by adding the salt this usually helps the problem and won't hurt it unless thou some of your readings are really bad. You may also have low oxygen levels or worse, flukes, parasites or other pathogen problems. Continue to monitor carefully their behavior and other other noticiable changes.

Good luck.
Koi Kichi
Al

I'm glad there's a thread on this. I have this issue sometimes with our largest Butterfly Koi. He's way bigger than everyone else (a little over a foot and a half long), and sometimes scares the crap out of me. I'll be out there and all of the sudden, SPLOOOSH!!!!!!!! Sometimes he can throw a good deal of water out of the pond.

Here's the deal though. I have perfect water quality (according to tests), PH, water hardness, all the Nitrites, Nitrates, and Ammonia are used up just as they're created... so basically they always read zero. He's kind of a scaredy fish, but what I'm guessing is he surges up so fast to grab (what he may think) is a piece of food, that he overcalculates the surface and just goes soaring out (this usually happens when it gets dark). Sometimes he stuns our other fish, because he turns so hard (to dive) after grabbing food, that his powerful tail whaps everyone around him. Hes the biggest fish, but man - what a ridiculous fish! hehe, we have some small guys, who just come up to the surface (when they see us) and sit like a bobber, mouths wide open) waiting for us to pile in the food .

Our pond is only 3' deep at the minimum, and 3.5' deep at the max. So since we're shy of the 4' perfect depth, I think it's a matter of size of fish strength/speed vs. size of pond. At least, that's what I'm hoping...

For the most part, my koi seem to do a lot of jumping when they're feeding. I have a mixture of lrg, med and sm koi and it's a real battle at dinnertime. I try to spread the food out so that everyone gets some, but the larger koi seem to just jump right over the big ones to eat everything in sight. There are other times, especially if one koi seems to find something to munch on, that the other koi want to find out what it is they're eating that they jump over eat other. Other than when food is involved, there's not much jumping going on in my pond.

I have had koi that jump just to get your attention. I have had koi that will swim into the skimmer if the lid was off to get the food that may have gone in there and than jump out of the skimmer back into the pond. Koi can jump a far distance and very high. I was giving a 6 inch koi from my pond to a friend once and in trying to net it he decided to jump. I was standing up right on my bridge and this fish cleared the top of my head. This fish jump about 8 ft high and landed 14 ft away from where he took off.

I would question your test kit as this is an older pond or you have exceded the limits of the pond.
Mike