I think that results will vary for Koi depending on region and water clarity.
Many folks around me have a few Koi in their game fish ponds, and the koi cannot seem to reproduce. The keys being the predator fish being already established and plentiful, and the water clarity reasonable for the predators to see the koi fry. This is my situation as well. I have 1 butterfly koi, and 3 standard koi, and for the past couple of years, no sign of any reproduction. (Thank God!)
My other fish are Walleye, Yellow Perch, and Black Crappie. The baby perch are voracious hunters, and go around in large fast schools. I cannot imagine much escaping them when they come upon it.
There is one pond in town that has been overrun by koi, and it is a muddy mess. I would guess that once it has been overrun, predator fish have a very difficult time seeing prey and getting handle on the koi population. The owner of this pond put koi in before anything else, and the koi own it now. The only way to deal with a pond in this condition is nuke it from orbit and start over, or seine it over and over and sell off the koi until empty.
I have never heard a good thing said about bullhead in a pond. Another pretty messy fish, stirring up the bottom.
Last edited by liquidsquid; 10/04/17 08:59 AM.
