My pond is about 8' by 20' and up to 5' deep, but it suffers from soft
edges.
The soil is very loose and soft and so my edges keep crumbling. This
makes
putting edging stone around the pond a real challenge.

Any suggestions?

I've thought about putting a ring of concrete around the edge of the pond
and then putting the slate edging stones on top of the concrete. I'm
thinking I'd need to put a layer 2-3 inches thick and have it extend about
two feet from the edge of the pond out into the yard so as to create a
stable edge.

Suggestions welcome. I have a nice big pond with a wonderful ecosystem
_in_ it...it just doesn't look all the great in the yard. Thanks.

Had the same problem the area under the waterfalls kept on collapsing due to
the wieght of the rock.
I used 12x24 paving stones as footings and then used cement blocks to build
the back wall of my pond. the 12x24 spread the load, I then used 8" block
for the first two courses, everything above this was 6" blocks. Backfilled
with cruched rock/sand mix. the wall was then covered in a double layer of
geotex (sp) fabric. then the liner, over which another layer of geotex under
the waterfall and rock garden rocks.

I am sorry I do not have any photos of the work, did not think it worth
while taking any.

ANO