Getting rid of unwanted koi, esp. large koi, can be really difficult.
You could also try FreeCycle.com. They don't let you give away pets, but I think fish might be an exception. I once offered koi on FreeCycle, and the moderators didn't scold me. Incidentally, I didn't give any away... In my listing, I said they person had to have a sizeable pond with filtration, etc. That eliminated many people right off the bat. Other people who asked for the fish never showed up to get them. So goes Freecycle, sometimes.
My ex found homes for several large koi by giving them to a snazzy local hotel, for their garden ponds.
So maybe you need to think outside the box... if an individual doesn't need or want them, perhaps a business, restaurant (many Chinese restaurants have fish ponds), hotel, etc. might be a good place to call.
Just don't turn him loose in a waterway!
