In uk.d-i-y, vortex2 wrote:
In the next couple of weeks we are seriously "upgrading" our garden pond to
be approx 15m^2 (is/was about 3 m^2).

Local herons seem to feed well from garden ponds, so historically we had
fruit cage netting covering ours to prevent them harvesting our fish. A
complete eyesore.

This may not help but... when we moved into this house there was a 3m^2
pond which soon lost all its fish to the herons. So we built an
additional 35m^2 pond. The herons visit daily, but get no fish, or not
enough to matter: we started off with twenty golden rudd in there and we
now have many hundreds. I suppose the species might make a difference
but I've always put it down to the depth: one metre in the middle, so
that the fish can lurk down there out of reach.

The herons do get frogs, though.

--
Mike Barnes