Appreciate all the input; I now realize there are more variables in the fish decision than I found in my initial casual research.
Here's my plan:
- expand the pond into the raised bed and make a shelf that extends ~8" below water level
If there were my project, given the slightly oriental character of the garden, I would make the pond larger in all directions, and include as long a stream as possible. I'd also want the pond to come up to the edge of the wooden deck (and if possible, even extend a ways underneath it). The skimmer could be hidden under the deck, where it would be well camouflaged. This also puts the skimmer at the opposite end of the pond from the water inlet, which is the ideal configuration.
So I'd go with something like this:
- have the liner extend up over the edge of the raised bed
- place 2 or 3 aqua blue boulders on the top shelf that extend higher than the top of the bed
- no stacked rocks - individual stones extending from the water to a few inches above the raised bed (or modify the raised bed to fit the rocks if need be)
You can make your rocks go farther still if you layer them one behind the other, as seen from your viewing area, but with gaps between them. The gaps can be filled with river rock, so the who area looks as if it's been periodically flooded.
- for edging: fold over the liner and backfill with gravel/mulch ensuring runoff flows down sides of bed and not into the pond
You may also want to include some flat rocks standing some ways back from the pond, set so that their tops are higher than the raised bed, this will effectively keep soil from the beds from flowing into the pond. It will also make the pond look like it's been carved out of rock into a low spot.
A few thousand years ago my lot was part of Lake Michigan; ~a foot under the topsoil is mostly sand and rock. Anyone with experience building shelves that maintain their form in sandy soil (or other tips for working in sandy soil) please let me know about your experience.
I had a similar problem, except that my "soil" was gravel and rock, rather than sand. It wouldn't hold a shape, so building conventional selves was out.
What I did was to over dig the whole area, creating more or less the shape I wanted, with more or less the correct depths. Then I laid the underlayment and liner (it was 65 mil roofing material, so very, very heavy!). Then, starting from the deepest point, I started laying my first row of rock. Once I had this row stable, I pulled back the liner and underlayment and scooped the loose gravel "soil" up against the back of the underlayment/liner combo to near the top of the first row of rocks. The rocks on the inside of the liner held up the loose gravel. Next, I put the liner back on top of the shelf thus created, and lay the next row of rocks some 20 cm or so back from the first one.
Thus, I built up the shelves using the rocks inside the pond as walls to hold the soil in place. In your case, you may have an easier job of building like this, as the sandy soil should hold its shape (especially if you wet it) a bit better than my piles of gravel did.
If you have old bricks or concrete pavers lying around, those can also be helpful in making your shelves. Just be sure to grind any sharp edges off them with an angle grinder so they won't make holes in your liner.
Cheers!
-Yael
