A heron is a long-legged bird known for stalking the margins of ponds. Every day a heron consumes 369gr of food, which is the equivalent of three 6-inch long Koi or 10 2-inch long goldfish. In spring, when a heron is feeding its young, it will collect twice this amount of food. You can prevent herons from fishing your ornamental pond using a variety of repellent methods.
Mark a circle around your pond that is 6 to 12 inches away from the water by dusting the ground with baker's flour. This is the location where you will put your fishing line perimeter. A heron cannot lean over a perimeter to fish at this distance.
Drive wooden stakes into the ground around the perimeter of your pond using a rubber mallet so that they stick above the soil by 12 to 24 inches.
Tie fishing line to the stakes so that it stretches between them. The line should be suspended above the ground at intervals of 12 and 18 inches.
Mark a circle around your pond that is 6 to 12 inches away from the water with baker's flour.
Drive stakes made of metal rebar halfway into the ground at the location where you have marked your circle. The rebar should have 12 to 24 inches of space sticking out of the ground.
Tie netting to these stakes so that it is suspended over your pond by 12 to 24 inches. The netting must be taut so that if a heron lands on it, it will not dip into the water. This will prevent the heron from spearing fish through the netting.
You can place a plastic heron into your pond to deter real herons. Herons are territorial and will not fish in areas where they think other birds are fishing. Other visual deterrents that may drive herons away include plastic reproductions of the bird's natural predators including plastic alligators or owls. You can also grow marginal plants around your pond or create a pond with few shallows that a heron can use. This will make the environment hostile to heron hunting.