I would be interested in hearing from other people regarding herons (and protecting against them). I have decided to roll back my net, have a plastic heron to hopefully protect my fish. Where I live there are many herons around, as there are lots of big ponds in the neighbourhood.
Some months ago I actually saw a heron by my pond eyeing up a snack before I chased him off.
The place I bought it from has a huge range of ponds, 3 of them tiered, 100m long and 10m wide !! He told me herons can take 30cm (12" fish) without too much difficulty.
We had a heron as a regular visitor to our little pond (only about 18 - 24 inches deep) He was able to wade in and take his pick.....
When we built this pond we have made it deep (6 ft) with straight sides. We have about 1ft of raised brickwork. This does not provide any way for the heron to step into the pond. and if he stands on the side then he only has a limited reach.
We still see the herons around but have not seen any by the new pond, we haven't lost any fish and we don't have a net over the pond or any plastic herons.
If you look up about herons on the RSPB site it does have quite a bit of useful info !
I had the fright of my life when I opened my curtain one morning and saw this jumbo jet of a heron taking off from my garden. Not taken any, but saw him a couple of times subsequent to that appearance.
Covered the shelf end on the pond with a net for a few weeks and invested in a plastic heron. Not seen him since.