By Faith Peppers
University of Georgia
The problem is at its peak in spring and early summer, when the herons feed their young, says David Pool, a koi expert with Tetra Pond, a water-gardening-products company in Blacksburg, Va.
Each day, Pool says, an adult heron needs about 13 ounces of food, or about three 6-inch koi or 10 2-inch goldfish. Herons take twice this amount when feeding their young.
They're generally shy birds, he says, and visit garden ponds when everything is quiet, usually early in the morning or in the evening.
Once the herons have found an easy source of food, such as colorful fish in a shallow pond, they'll return until they've taken most of the fish.
To keep feathered fish burglars out of your koi pond, Pool offers these tips:
Netting. Suspending a net 6 to 12 inches above the pond surface will prevent the heron from attacking your fish. Make sure the net is taut and can't fall into the pond if the heron tries to land on it and spear the fish through it. This may not be the best-looking solution. But it's by far the most effective.
Perimeter Wire. Herons don't normally land directly in the pond, as they will scare the fish. Instead, they land in the garden and stalk toward the water. Suspend strong fishing line 12 to 18 inches above the ground around the pond to stop the heron from reaching its destination. Put the fishing line 6 to 12 inches back from the pond to prevent the heron leaning over the barrier to catch the fish.
Heron Scarers. A number of commercial scarers work in different ways. Some use a trip wire and produce a loud noise and, in some cases, a visual deterrent to scare the heron away. Some use sound inaudible to human ears. Others detect the heron with infrared light and scare it away by spraying a high- pressure jet of water. Remember, these can also be activated by guests visiting your yard.
Plastic Herons. These are popular. Their success is based on the principle that herons are territorial and won't feed close to another heron. Unfortunately, this isn't completely effective anytime, especially in late winter and early spring when herons search for a mate. Then it may actually attract herons to your pond.
Pond Design. When designing your pond, it's possible to make life tough for herons. Dense growths of tall plants or shrubs around the pond will limit their access to the water. Making the pond side steep and the water 8 to 12 inches below the edge of the pond will also help, because the heron won't be able to reach the fish.
If you do lose some fish, don't resort to harming or killing the herons. They're protected species.