| Don
The air supply to the air domes at that depth will suffer using some of the traditional methods of air delivery. But there are pumps that will deliver the air to 35 feet or more without a problem.
As far as catching the Koi in a deep pond, the same holds true for a very large pond as well. It does pose problems, especially if you intend to show the fish, or find the need to treat one.
I find that 5-7 feet is a great depth, and even 4 feet is acceptable if you do not intend to show the fish.
Best
d |