As any koi or goldfish garden owner knows, an unwelcome visit from a hungry heron can completely annihilate a fish population.
Furthermore, heron activity can create additional problems, including the transfer of fish diseases, traumatic stress on the surviving fish, and damage to the pond liner.
If you have ever encountered one of these massive birds of prey, you know that they are tenacious and extremely persistent.
Once they have discovered your pond, they can be expected to return again and again until they have killed or eaten all of your prized fish.
Fortunately, there are several measures you can take to protect your koi and goldfish from these aggressive avian predators.
Create a barrier over your pond The most effective method of protecting your fish from heron predation is to cover your pond with netting.
However, over-the-pond netting is not invisible and can distract from the aesthetic appearance of the pond.
When appearance is an issue, some pond owners will opt to use pond netting after the threat has been discovered to deter future visits.
Create a hiding place for your fish Fish are very reactive to herons and will instinctively try to hide when they recognize their presence.
Floating plants, both natural and artificial, make excellent hiding places.
You can also try a tunnel-shaped net that rests securely on the bottom of your pond, available at pond supply stores.
Discourage the heron from visiting your pond Herons are territorial creatures and are known to fish alone.
That's why imitation herons, in the form of statues, are a popular fixture near many koi ponds.
However, herons are much too clever to be fooled by a motionless "bird", and usually return after the ruse has been discovered.
A better option is a motion-activated device that emits water or sound when the heron approaches.
These devices have been shown to be very effective at frightening herons away and discouraging their return.
The method you use to protect your pond will depend on the size, depth, and location.
To get the best results, you may need to combine several of these techniques.