Stepping this back to basics.
Why do you want catfish?
The pond is 100ft diameter and 13 ft deep, the chances of ever seeing a catfish in there are zero to none existent even for any of the larger ones, including gold varieties of the same. The chances of seeing koi frequently are pretty low already, without the added threat of adding something to potentially grow to a size to be a threat to them.
Let us know more about what you want and why and other ideas may come to mind but for now, I just don’t get it.