I use 4 foot rebar and 3 strands of 50 pd. fishing line spaced 1 foot apart between the rebar.
It has worked for three seasons so far.

Heron have long legs and are accustom to walking over objects like tree branches and vegetation. I donÂt think fishing line around the perimeter of your pond will stop them from entering. A series of fishing lines running across the pond would prevent a heron from maneuvering within the pond and is more likely to keep them away.

Last year I lost all my fish in a single night/early morning to a heron. The place that sells fish also sells netting to put over the pond each night but there must be a better solution. Given enough floating plants is it possible for the fish to hide? Perhaps an under water cave they could hide in? I don't want to do something that will detract from the beauty of the pond.

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I watched a blue heron walk around my pond and every time he tried to approach the pond, he would bump into the line and eventually gave up.
My line is three rows and three feet tall. Any shorter and the heron can step over it.
The rebar is spaced about 10 feet apart. I did not make that clear in the first post.
My pond is too large to net.
The line is see through so it does not detract from the look of the pond that much.

Yes it works . I just tried it this year for the first time . Havent seen the bird since early May . I used 3 foot poles of bamboo stuck in the ground and ran two rows regular white string across . My pond was too deep for the bird to walk in anyway but this will keep it from bending its neck over the strings . Works great and looks a little better than having a net over the pond . Now all my frogs are safe too . Rick

JohnK is right, the line should be higher than a foot tall.
Lsst has the right height obviously, strung at three feet tall, it is doing the job keeping the heron away from the pond.
I have a decoy heron, it stood in various spots in the pond for years and no heron problems.

So I figured it was doing the job, until one day I heard something clomping around on our patio deck's roof in the very early morning. I thought it was a raccoon, with the noise it was making? It was a great blue heron. I guess from that vantage point it figured it could look over the smorgasbord and select it's next meal.

Down from the roof it dropped and walked right passed the decoy, without as much as a "how ya doin'", and was about to go for breakfast, when I scared him/her away.

After that incident,I reverted back to having the fishing line strung around the yard for a week or so with pieces of coloured tape tied to it.
The heron would stand up on my neighbour's roof and study my backyard, but never, as far as I know, attempted to venture down to the pond.
I have not seen a heron since and the decoy heron is still waiting to get lucky!!??
"Horton"

Just bought my annual reel of fish line yesterday! We usually wrap it around 2' pieces of rebar that are stuck 6" into the ground. It goes around the pond perimeter and also crisscrosses over the shallow areas. When Ms. Slomo lands and walks up to the pond edge, she bumps into something she doesn't see, and it apparently confuses her enough and she leaves.
We only lost fish to a heron once, and have used fish line ever since. Not even all the time. But Ms. Slomo has been checking out the joint lately, so now we're putting it up again.
Once we have enough water hyacinths and lily pads, the fish can hide better than in spring, and then we take the line down. Since we are forever tripping over it ourselves as well...

:) Mary

We lost fish three years ago. I put fishing line (one strand 16" high) around pond and haven't had a problem since (knock on wood).

I not convinced a fishing line fence of any height will keep a heron from entering a pond. I know they like to land near the pond and walk in, but they are also capable of landing in a pond. IÂve linked a photo (below) from Wikipedia showing a heron perched on top of a fine tipped rock. ItÂs actually gripping the rock with its claws. If a heron can land on that rock, I think it could land on top of a potted plant or pump hose within the pond.

On the other hand, I think crisscrossed line across the pond is going to cause problems for the bird. A blue heron should have difficulty getting its 3-4 foot body and 5 foot plus wingspan into a pond that has a series of lines crossing over it.

Here is a link that might be useful: Great Blue Heron

I use a net. I just feel safer after numerous heron attacks. It's not that bad - virtually invisible until you get close. I don't like the idea of fishing line because we have a dog who would run right into it and I don't want to hurt him. Also, we like to get into the pond periodically to fertilize and maintain the plants. All we have to do it take off the net. I don't want to mess with fishing line. We've come up with a pretty good system I think. We drive 4 foot stakes in the pond (3 feet when done) and secure the net to the tops and sides of the stakes keeping it about 6 inches from the bottom so the frogs and birds still have access.

But I think the line would probably work if that's the way you want to go. I fence our pond over winter so no one accidentally steps into it - we can get many feet of snow in a season and the fence gives me a guideline since it's right off our patio. Also keeps the dog off it. By the time I can get the net on in the spring, no herons have figured out how to cross the fence - however that hasn't stopped them from visiting. I'm sure they're taking notes! Our fencing is 2-1/2 feet tall. Be sure you string the line as close to the edges of your pond as you can. If the heron can fly into your pond and land on something, the line will be useless.

As well as a criss-crossed grid of line around the pond at about 20" height, I have an overhead grid of line strung between the house and the side and back hedges. I'm a few blocks from the ocean, and used to get a lot of herons, but haven't lost a fish since we put in the overhead grid.
Good luck!

Ronaye, welcome back! It has been a long time since we have seen a post from you.
This has been a real home coming week, with David [DRH],Andrea [Ademink] and now you posting again.
Your insight and experience have been missed around here.
Hope you and the pond are well.
"Horton"