My folks have one. I hate the thing, really! It's POA squared in my opinion. Birds come down and feed off the koi, creating a sort of fishy genocide. So they put chicken wire around the pond, resulting in a very ugly sight...
Now frogs have invaded the pond, so through the night, starting at sunset, all that can be heard in the yard are frogs engaging in their frog talk.
Plus the pump, the loud splashing water, the fact that small animals; dogs, rodents, etc, see it and immediately want to take a dip...
Also misquitoes. Their koi pond is a magnet for the pests...
Oh, and theirs is about the same size as what you're planning - in fact, I think their koi pond is a bit smaller.
If this were my endeavor, I'd either install a nice-sized fountain, in which you could put some fish, or a swimming pool, in which you can put yourself.
