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Small wildlife pond. To dirt or not to dirt, that is the question ...

Poppins

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14 Oct 2023
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London
... lets face it, it won't be the only one.

So, an ambition that has been brewing since before the unexpected and not particularly planned aquarium aquisition <obsession> was to construct a wildlife pond on our allotment plot. The rules allow up to 6m perimeter (including beach/bog) and up to 60cm depth. I am thinking of a roughly 2m x 1m rounded rectangle/oval, about half of it (crosswise) to be a sloped beach/shallow planting area, the other half to be a deeper well (for improved temperature regulation and perhaps overwintering amphibians) surrounded by a planting shelf ( I'm probably making a rod for my own back lining-wise here aren't I, kind of like the regret you have wrapping presents late on Christmas Eve when you realise you've yet again strayed from cuboid gifts). No electricity supply, so no pumps/filters (though I might consider a solar powered fountain to deter mosquito larvae), and no fish because I want to encourage amphibians and insects. It will be in a site that gets pretty full sun (the only shaded areas are under trees so leaves and roots would be a nightmare)

Here's a sketch, beach on the right, well and planting shelf on the left ... please excuse the spellings, this was me designing it with my 6 year old son!

IMG_8908.jpg


As anyone who has slogged through my aquarium journal (Absolute Beginner’s Descent into Madness with a Superfish Scaper 90L, sorry overdue an update, I promise there will be one soon) will know, I have a tendency to suffer from overthinking and going down big internet "research" rabbit holes and ... whooo-boy ... there's almost as much conflicting advice out there about ponds as there are with aquariums isn't there? 😩

I'm sure I'll have more indecisions and confusions along the way (I'll try and journal this one from the start this time, rather than retrospectively) but the one that's doing my head in at the moment is what (if anything) to put on top of the liner.

There are <some> <people> who advocate laying a secondary layer of fleece liner on top of the waterproof liner, then covering that with about 5-10cm of subsoil from the deepest part of the excavation, completely hiding the liner and allowing you to plant directly into the soil.

There are <others> who say this is a bad idea ... and some who are even opposed to <any rocks or gravel> (although i get the impression that is more with fish ponds)

My instinct is of course towards the more natural look which would presumably allow for a more complete ecosystem ... but it does seem to invite a potential world of pain (harder to move/control/maintain plants, possible nutrient soup, possibility of brown water that'll never clear, extra engineering required to stop all the mud sliding down into the well, etc).

So I'm thinking maybe a bit of a hodge podge ... cobbles and gravel on the beach, a loose submerged stone "wall" at the bottom of the beach to stop these falling into the well, maybe just bare liner on the planting shelves (plants in baskets) though with loose bricks/stone around the edge to hold up/disguise the liner/provide nooks and crannies, maybe sand at the bottom of the well because ... well ... just because?

It won't look quite as natural/pretty, but an allotment is of course a somewhat more utilitarian aesthetic than a garden, with bits of plastic, timber and metal everywhere you look, and it's not like we'll be there every day to admire it (unlike in a garden) so perhaps that doesn't matter and I should just go for the easy option (and let the "natural" look build up over time with sediment and growth)

And as for those who say don't put any gravel or rocks in or around your pond or it'll end in tears ... well ... I'm hoping I can safely ignore them.

Any thoughts or advice from you wise people?

Many thanks.
 
Hi all,
who advocate laying a secondary layer of fleece liner on top of the waterproof liner, then covering that with about 5-10cm of subsoil from the deepest part of the excavation, completely hiding the liner and allowing you to plant directly into the soil.

There are <others> who say this is a bad idea ... and some who are even opposed to <any rocks or gravel> (although i get the impression that is more with fish ponds)
The issue you have is the tussle between a quick win and longer term stability.
So I'm thinking maybe a bit of a hodge podge ... cobbles and gravel on the beach, a loose submerged stone "wall" at the bottom of the beach to stop these falling into the well, maybe just bare liner on the planting shelves (plants in baskets) though with loose bricks/stone around the edge to hold up/disguise the liner/provide nooks and crannies, maybe sand at the bottom of the well because ... well ... just because?
I didn't put any soil in my pond (below) when I built it, I just chucked all the rocks I'd excavated back in to form terraces and topped it up with rainwater. It was great for a couple of years, but I <"couldn't stop it filling in"> and it <"ended up like this">.

southern_hawker-jpg.jpg


Personally I wouldn't add any soil. It will aid plant establishment and growth, but <"plant growth is the issue going forward"> and it will be really difficult to maintain any clear water.

I think of it a bit like planting a hedge in your garden. If you plant Leyland Cypress (Cupressus x leylandii),
  • six months later you have a hedge, and
  • six years after that you have a row of <"fairly substantial trees"> that you can't prune, or
  • you have spent a lot of time maintaining your hedge and that maintenance requirement is ongoing for ever.
If plant Hornbeam (Carpinus betulus) it takes longer to form a hedge, but after that it is all plain sailing.

cheers Darrel
 
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Thanks for your helpful responses. In the end I didn't add soil, but I did use a black overlay on top of the liner and added sand in the shallow area underneath the cobbles.

I'm planning to start a proper journal of it, but here is a preview ...

IMG_9267.jpeg


It was dug and filled a few weeks ago but is still a definite work in progress (not least because I need to go back to the builder's yard for more sandstone bricks, cobbles and a few bigger rocks). Had a greenwater algae boom and bust so now the bottom is covered in a greeny-brown sludge, not sure if it's alive (a different form of algae) or dead (the remains of the greenwater algae after it used up all its food source).
 
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