Blue Heron

Koi Predators

The worst thing to happen to a koi pond owner is to start losing fish to a predator. The early signs to this is the koi are unusually spooked when you go to feed them. There are fish that seemed to disappear with no trace. By the time you see a predator they have already wreaked havoc on your fish.

I have had a personal experience with this matter. I had lost several fish from my pond before I spotted a 4 foot tall blue heron in my pond. Actually, my daughter saw the great bird before I did. I had done some research and suspected the blue heron. Both my wife and daughter thought I was crazy until they saw the bird standing in the middle of my stream area. I tried several things to keep the bird away. I put up motion lights for the night, a fake snake, and an owl. I started getting up before daylight to try to catch this bird. One would land on the corner of my neighbors roof and wait to make sure the coast was clear before landing in my yard and making the march to my pond. These birds are wiley and have a field of vision of over 300°. Any movement at all will put them into flight. They are also persistent. Any decoy used to scare them away, including floating alligator and the motion activated sprinkler, will only work for a short time before they get used to and ignore it. Netting the pond in the early spring will keep the blue heron from getting to the koi if it is well staked around the edges. The heron will soon learn and go somewhere else for food. After a couple of weeks the net can be removed.


Other koi predators are the racoon and weasels. Raccoons will mainly feed at night and can be a real problem in suburban areas. Most frogs do not pose a problem in a koi pond. Larger frogs, such as bullfrogs, can eat smaller koi. As soon as you see large tadpoles in your pond, relocate them as soon as possible. Frogs tend to attract snakes. Another koi predator can be the neighborhood cat.

Dealing With Koi Predators

Pond construction can have a lot of influence on keeping your fish safe from predators. Having a large deep area, 30 inches or more, where the koi can go to if startled is a must. Build the sides steep and have a rock ledge well above the water line. When there is a stream that flows in the the deeper part make steep drop offs. Don't create a shallow pool where the koi are semi-trapped away from the deeper pool. Frogs can be caught and relocated with a flash light and net at night. It works best with two people, one to shine the light while the other nets the frog. Raccoons can be kept out with an electric fence. The only foolproof method of keeping the blue heron out is a watch dog of medium size or larger. I have a Staffordshire Bull Terrier mix that I rescued from an animal shelter. I got him when he was six months old last spring and kept him outside the rest of the summer and fall. He keeps everything out of the backyard, including snakes. I still have to catch the frogs. I now let him in at nights and have still not had any predators so far.