which turtle?

I am still trying to find a turtle that I can add to my pond. I found out the red-eared slider wanders and there is no way to put a fence on top of the rock retaining walls for my pond.
Can anyone tell me about the Painted Turtles or the Spotted Turtles? My smallest koi is about 7" long and largest is about 14" long. Will these 2 types of turtles try to attack them? The Painted Turtles get to be about 10" long but the Spotted Turtles only get up to 4" long.

Any kind of turtle in your pond will eat your fish and tear up your plants.