And an old man repeating himself says...
No matter what type of ponds you build, many of those folks will be entranced and intoxicated by the beauty of the fish. Providing a proper pond, not a compromise, will keep you from killing pets.
I love the comment on the pond landscapers board about killing a few fish being OK, after all they cull so many.

Sheesh, girlie. I understand that cheap fish can be replaced every year like Frank says, but kids cry about Wanda and Shark and Harold and Specs and Fugly and all the other fish that grasp hearts and can't be replaced. We've all seen plenty of ugly fish still in a pond because you or somebody in your family loves it.
Noone has yet touched on the fiasco brewing when Kodama fish go to RWG store and then in bags to hybrid ponds. Some advice? Fish biologists are cheap. Koi immersed fish biologists cost only slightly more. Get a good one. Sell healthy fish.
Mickey the windowman