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Hand building a clay pond

Printed From: Reptiles and Amphibians of the UK
Category: General
Forum Name: Wildlife Gardening
Forum Description: For discussion about wildlife (especially amphibian and reptile) gardening
Printed Date: 26 Oct 2020 at 9:54am
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Topic: Hand building a clay pond
Posted By: GemmaJF
Subject: Hand building a clay pond
Date Posted: 19 Sep 2011 at 2:15pm
Hi all,

Has anyone any experience of forming a small clay pond by hand along the lines of the old dew ponds?

I'm up to speed with doing this on a large scale these days, it involves a JCB, a supply of suitable clay delivered and and some form of mechanical compactor, geofabrics etc.

This is fine for building a GCN pond during a mitigation, but my needs are a little less demanding.

We have what was an established wildlife pond. It's not large but not that small either. Interestingly it never did dry up completely long after the PVC liner perished. I remember well only digging so far originally, well because I hit very heavy clay. 

The idea now is to remove all the plant shelves I originally put in, make it a gentle gradient and line with the naturally occurring clay at the bottom of the pond. The species to benefit are our smooth newt population.

Any tips or thoughts etc appreciated. I'm particularly concerned regarding capillary leaching of water as there will be a reasonably deep top soil layer surrounding the pond. I'm also prepared to the line with an artificial liner if it doesn't all workout, it would though be very nice indeed to form a pond without the need of an artificial liner.

Posted By: Caleb
Date Posted: 20 Sep 2011 at 9:47am
I don't have any hands-on experience, but I did look into it a while ago for volunteer project with a derelict school pond, about 10m x 5m. In the end, it was decided against, mainly because of the amount of labour needed, and difficulty in finding a clay supplier.

If I remember right, it was recommended (probably by BTCV) to use a very gentle gradient, apply clay about a foot deep, take one man-hour per square foot to puddle it, and not to let it dry out under any circumstances.

This worked out to about 15 tonnes of clay, and 550 man-hours of puddling- that's when a liner started looking more appealing. We didn't get as far as thinking about capillary barriers.

The shallow gradient needed means that it would have to be a pretty big pond to get any reasonable depth- but then you'd have to dig a pretty big hole to get enough clay anyway.

Sounds like a fantastic project, but not the sort of thing that could be done in a weekend...

Posted By: GemmaJF
Date Posted: 20 Sep 2011 at 10:31am
Cheers Caleb very helpful info. I'm mostly considering the project to battle the winter blues, the more time I spend outside the happier I am, but mostly in the winters I hibernate and stay indoors, then get depressed. Puddling a pond on freezing cold days actually has some appeal compared to depression lol.

I think my main problem will be to get a gentle gradient and reasonable depth. here is the pond as it appears at the moment:

The water in the sump has sat there all summer which sparked the idea that  a natural pond was possible. Max dimensions are 5.4m x 4.6m current max depth is 60cm. Standing water is about 20cm at deepest point. I'm pretty much constrained to the max dimensions as the pond already takes up as much available space as possible.

I think the issue is going to be that to dig out the clay from the bottom, the pond is going to get deeper and thus the sides steeper, making it very difficult to produce the gentle gradient required. 

I guess one option would be to go for a sunken pond, thus avoiding capillary action of the top soil  and making it easier to form a gentle gradient. Not entirely sure if that is what I would want though, as seeing water in the garden is part of the appeal of a pond for me.

Posted By: Hawley
Date Posted: 21 Sep 2011 at 1:40pm
You could try asking Chris Rumming, he knows a lot about ponds. His website is -  

Posted By: Caleb
Date Posted: 22 Sep 2011 at 9:11am
Originally posted by GemmaJF GemmaJF wrote:

I think the issue is going to be that to dig out the clay from the bottom, the pond is going to get deeper and thus the sides steeper, making it very difficult to produce the gentle gradient required. 

In theory, you could dig out the whole pond to depth, and put the topsoil back under the clay. Sounds like a lot of work, though.

I've just a found a section on puddling in 'The Pond Book' by Valerie Porter, which makes it sound a bit easier than I'd been led to believe:

Posted By: GemmaJF
Date Posted: 22 Sep 2011 at 9:45pm
Cheers Caleb. The thought of digging out the top soil, then digging out the clay, filling with top soil and lining with the clay might just be the answer. I was pondering this myself yesterday.

I like Valerie's method, sounds much more doable than other stuff I've read and I think is exactly what I was looking for, a scaled-down method for a garden pond. Does she mention anywhere the gradient? I don't know why but for some reason I think it might not need to be so shallow on a smaller scale. Not sure why I think this, perhaps something I read a long time ago.

I'll go for it I think and see what I end up with. Not sure where I would find soot these days though, perhaps I can find a local chimney sweep.

Posted By: Caleb
Date Posted: 26 Sep 2011 at 3:32pm
Originally posted by GemmaJF GemmaJF wrote:

Does she mention anywhere the gradient?

She says that clay is suitable for 'any shape or gradient'. Presumably the more vertical it gets, the more difficult it will be to compress it properly...

Posted By: GemmaJF
Date Posted: 26 Sep 2011 at 5:59pm
Excellent, I'll be getting on a bit with it tomorrow, shall post up some progress as I go along.

Posted By: herpetologic2
Date Posted: 26 Sep 2011 at 6:07pm
Do you need the depth? would it be possible to make it shallower? reprofile the shape of the pond perhaps and re puddle?

Report your sightings to the Record Pool" rel="nofollow -

Posted By: Suzy
Date Posted: 26 Sep 2011 at 7:01pm
I think traditionally these ponds were like massive saucers - i.e. round and shallow. They must have overflowed with rain at times but often there was water in the centre but not right to the edges where the grass grew. The edges were kept plastic by the sheep's feet trampling as they walked to get to the water. At night the water vapour/mist condensed on this cold shiny surface and trickled down into the pond. It does seem like some sort of magic but these ponds used to hold water even in the driest summers when spring fed ponds had dried up.
The ponds are supposedly good for newts as fish can't get along in them as they are not very permanent. How this quite squares up with always holding water I'm not sure!
My brother remembers a GCN dewpond in Dorset being ruined by the National Trust who dug it all out to improve it and after that it never held water and all the GCNs disappeared!
Lime was often put under the pond to stop burrowing earthworms destroying the clay liner.


Posted By: GemmaJF
Date Posted: 26 Sep 2011 at 8:27pm
The problem with the depth Jon, is I need to dig the clay out of the ground (which is going to make it deeper than it already is), there is the option of digging out the clay, back filling with the remaining topsoil and then puddling. I think first up I'll get the top soil out and see just what I've got to play with.

Yep Suz, I think this is just how they were. We have what remains of one in the field right behind us. It's never held water since I've lived here other than after very heavy rain, but my husband has said it did hold water up to about 20 years ago. It looks very much still like a massive saucer, despite having now been ploughed many times. A look on Google Earth still reveals the shape very well.

Posted By: GemmaJF
Date Posted: 13 Sep 2012 at 1:34am
Just a quick update, the clay pond was too ambitious by far. When I started work on it last year even with machinery it was next to impossible.

So the pond sat for a year as a kind of shallow crater.

I'll be starting work on it again as soon as the reptile activity ceases for the winter in the wildlife garden, the plan now is simply to re-profile it and to put in a liner.

It seems I'm not very good at replicating a herd of sheep lol.

Out of interest the 'old dew pond' in the field mentioned in the post above did hold water for many months this year (For the first time in at least 10 years), plenty of it during the heavy rains this summer, so with any luck the local newts still have a breeding site this year. 

Posted By: GemmaJF
Date Posted: 24 Feb 2014 at 4:08pm
Just a new update on this topic. The pond is still just a crater, now an overgrown crater!

Further research has turned up a dried Sodium Bentonite supplier in the UK. This should provide a natural solution so the clay pond project is alive again! 

The Bentonite stuff is a puddling clay, just add water and it will expand to 10 times it's volume. It's low permeability and appears to be the ideal solution.

This time I'm waiting for dry weather, it will be a mid summer project as before we just got bogged down in the wet existing clay and it was hopeless trying to complete the project. (This I've now found was my first mistake lol).

Now the plan is to buy a large pallet of Sodium Bentonite (Fuller's Earth) and hire a plate compactor and possibly a cement mixer. More updates when work gets underway!

Posted By: GemmaJF
Date Posted: 01 Jul 2014 at 12:33pm
Finally getting going with the clay pond project. I had several aborted attempts to get a cultivator working on the clay in the past. Usually it ended up completely bogged down and I burnt out a drive belt in the past trying to break the stuff up. Finally though at the weekend it had dried out sufficiently from the winter to get a successful go at it. The surface had of course managed to go rock hard in the sun as it dried out, but with an evening of heavy rain the night before I finally got the cultivator to break up the soil:

uploads/21750/IMG_8322.jpg" rel="nofollow">

I'll be ordering the clay in the next few days, so updates to follow. 

I'm going for a very simple saucer shape as is traditional with clay ponds. I've never really been a fan of shelves in ponds as it pretty much seems with gentle slopes one gets an infinite variation in depth for plants. So construction will be kept as straightforward as possible.

Posted By: GemmaJF
Date Posted: 01 Jul 2014 at 3:15pm
Sodium Bentonite clay has been ordered from:" rel="nofollow -

I calculated the amount as follows:

Pond is 5 meters across and vaguely round. So the area is pi by the radius squared. The square of the radius of 2.5 m is 6.25 m and multiplied by pi I get 19.63 meters square, which is near enough 20 meters square to me. I'm not really figuring in that it is a shallow dish, as in real terms it is practically going to be the same as if it was just a circle drawn on the ground.

1 25 kg bag of clay covers 1 square meter with 5 cm of PURE clay. So I would need 20 bags to cover the 20 meters to this depth.

However, I'll be mixing the clay with some of the soil that comes out of the pond. I'm guessing a mix of 1 part clay (wet) to 2 parts soils by volume will be perfect to seal the pond and ensure it is self sealing in the future. This means if I have 20 bags of clay, I get 20 meters square covered with 15 cm of clay/soil mix at a ratio of around 30 percent Sodium bentonite. This fits with the guidance posted by Caleb and information I've gleaned elsewhere.

So that's half a ton of Sodium Bentonite (20 packs) that I've ordered.

I found this page that describes a test that the soil to clay mix is correct which uses a bucket with some holes. There is also some general information." rel="nofollow -

When the clay arrives I'll do the test and if all is well hire a cement mixer to mix the soil and clay and a plate compactor to do the puddling.

I feel somewhat fortune that the calculations came out very easily, just luck that the pond was already the correct size exactly for a 20 pack pallet of clay. Smile

Suppose I better start digging out all that broken up soil whilst waiting for the clay to be delivered.....

Posted By: Tom Omlette
Date Posted: 01 Jul 2014 at 10:06pm
hard work gemma but worth it. will you still be able to observe your lizards with the pond there?


Posted By: Suzy
Date Posted: 02 Jul 2014 at 12:05am
Ooh Gemma sounds a fun project! When we moved to this house 25 years ago we were surprised to find we were on clay. Our other house in the same town had very light soil. Our new neighbour told us that with the clay you need to get on it in the spring when it was just right...too early and you could hardly lift your spade, too late and it had baked like concrete - so I smiled when I read yours had gone rock hard in the sun!
Good luck with it and look forward to progress reports.


Posted By: GemmaJF
Date Posted: 02 Jul 2014 at 9:31am
Yep Suz, that's exactly what our clay is like, either waterlogged and too heavy to work or set like concrete!

The plan Tim for viewing the lizards is to have some raised decking around the far side of the pond. I should gain about 1/2 a foot at the edge when the clay is added too. The decking idea seems to have lots of benefits. It will give me access to the log piles to photograph lizards, let me view the pond from the far side and also give an open basking platform for reptiles that won't get completely swamped by weeds in the summer. It will also provide hiding places for all the animals underneath and give me access even in the wettest winters when often the wildlife garden becomes one huge mud pie!

The grassy square on the left will also be decked and have a nice garden bench to sit on. I might even get the time to sit down one evening and start reading Richard's book there! (I live in hope lol)

Posted By: GemmaJF
Date Posted: 07 Jul 2014 at 2:30pm
Pallet of clay has arrived:

This morning we removed 10 barrow loads of soil from the pond, most of this was lumpy bits of clay and is being used to level parts of the garden. What is left is finer and will be sieved to produce a pile of fine soil with no stones for mixing with the clay. Fortunately using a cultivator brings most of the lumps and big stones to the surface, so raking it off to leave finer stuff is fairly easy to do.

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The next session of soil removal should see the center starting to drop as we'll be taking material from the middle of the pond to form the dish shape.

I should mention that I have a decrepit back, so I'm getting a lot of help from my son with moving the soil and clay etc, so credit to him for most of the hard work involved. Smile

It has occurred to me one way forward would be to mix the Sodium Bentonite clay directly into the soil with the cultivator. I think on a larger pond this would be a great way to do it once a shallow dish is formed. With a relatively small pond though, we are going to first remove the soil, mix it in a cement mixer with the puddling clay and then put it back in. More work but I think I'll get much more control over the depth of the clay lining and the proportion of clay to soil working the hard way.

Posted By: GemmaJF
Date Posted: 11 Aug 2014 at 7:24pm
Since the work in July we had a few major thunderstorms and work was a bit hit and miss when we could get on the clay. I would guess at least another 30-40 barrow loads of soil has now been removed.

We are running out of summer now and though ideally we would be looking for several days without rain to line the pond, well we would be waiting until next year! 

So today was work on it whatever condition it was in. This is what we found this morning:

uploads/21750/Pond_01_Aug.jpg" rel="nofollow">

Clearly it had decided it wasn't waiting for the sodium bentonite liner and wanted to be a pond already. Confused

Under all that water was broken up clay (hence the drowned cultivator in the middle of the pond.) Seemed like the best way to deal with it all was to hire a submersible pump and pump out as much water as possible. 

The next part was fairly unorthodox, we couldn't dig the clay, partly because it was far to heavy when wet and also because it would just stick to the spade/shovel in a hopeless way. So we resorted to collecting up lumps of the clay in our fingers (sometimes having to literally tear at it with bare fingers in places), rolling it up into balls like dough and then slinging it at the sides of the pond. All this whilst standing at times in a foot or more of water. Of course we had several heavy showers of rain throughout the day too to add to the enjoyment.

It paid off though, by the end of playtime this was the result:

uploads/21750/Pond_03_Aug.jpg" rel="nofollow">

So we have our dish shape, this is all from naturally occurring clay from the hole we dug. The smooth finish was achieved with a broom, pushing the water/clay mix up the sides to smooth it all out.

We are hoping for no rain tomorrow morning  so we can push on with the sodium bentonite liner.

Have to admit it was kind of fun in a bizarre way, my sister would be proud of me, she taught me how to make mud pies when I was little and this has got to be the biggest mud pie I've ever made that didn't involve a JCB. Wink

Posted By: will
Date Posted: 11 Aug 2014 at 8:35pm
Fabulous effort so far, keep us updated Gemma Clap

Posted By: Suzy
Date Posted: 12 Aug 2014 at 12:01am
Excellent Gemma! I can imagine it. I'm surprised you kept upright - the stuff is so slippery.
Good luck!


Posted By: GemmaJF
Date Posted: 12 Aug 2014 at 8:57pm
We didn't always keep upright Suz! Sometimes I just gave up and laid in the stuff whilst working!

Today was a massive effort to get all the Sodium Bentonite in before the forecast rain arrived. Started out by hiring a cement mixer and wacker plate thingy. 

The first ten bags of Sodium Bentonite (there were 20 in all) were mixed with dry soil dug from the pond.  The Bentonite is the grey looking stuff, out of the bags it is remarkably like cat litter.  The mixture was spread over all the sticky wet naturally occurring clay from yesterday.

That took the morning to do.

It started to be obvious the top edge would need some extra attention, so five bags of the Bentonite got mixed dry with the soil and then put in a bucket and thoroughly soaked. This was so a top lip could be formed using a trowel.  This top edge can be seen being started below. I went right round the pond doing this - twice!

We now had five bags left and the threat of rain. Some sources say the Bentonite should be mixed with soil, others that the ideal is actually pure Bentonite. So we compromised and flung four bags worth over what we had to give a uniform coverage.

Now the fun bit, add water:

and more water....

and more...

I then went in and had a bath, started to process the above pictures and it's still not filled up. It's been going for hours now! I wanted a fairly big pond, but realised it was over half filled and still had at least 18 inches to go!

I've held back one bag of the Bentonite in case we ever need to do a repair. There is also a bucket full of the wet mix for the morning when the water has  found a natural level to fill in any low bits of the edge.

In all not too bad a job, and we got the Bentonite in just before the first shower this afternoon.

I'm not overly keen on the grey, it reminds me a bit too much of commercial projects I've worked on that involved balancing ponds, so the plan is to throw plenty of sloppy Essex clay and some top soil in the water over the next few days to naturalise the look more.

Posted By: Tom Omlette
Date Posted: 12 Aug 2014 at 9:31pm

Posted By: Suzy
Date Posted: 12 Aug 2014 at 10:00pm
It's looking good Gemma. Hope the creatures appreciate the hard work.


Posted By: GemmaJF
Date Posted: 12 Aug 2014 at 11:26pm
Thanks Tim!

Can't wait to spot the first to visit Suz, be it four legged, no legged 6 or more legged, they are all welcome Smile

Just went and checked the water level, it's still filling up, about another 6-8 inches to go.

Posted By: Tom Omlette
Date Posted: 12 Aug 2014 at 11:31pm
what do you reckon will be the first visitor/resident? frogs are pretty quick but you don't have many around you do you. probably an invert. i'll go for pond skater.

Posted By: GemmaJF
Date Posted: 13 Aug 2014 at 7:16am
Pond skater would be a good bet Tim, or perhaps a water beetle as they were pretty quick to find the pond the first time around.

Was up early like an excited kid on Christmas day this morning! I switched off the hose at midnight last night with a few inches of water left to go. It hasn't dropped a millimeter in depth over night, so all is looking good. Hose is back on for the final fill, I'll be adding the natural clay to the water for the colour change this morning. Smile

Posted By: GemmaJF
Date Posted: 13 Aug 2014 at 6:19pm
This is how it looked this morning, still needing a few more inches of water:

uploads/21750/Pond_13-Aug_01.jpg" rel="nofollow">

End of today, with lots of soil added:

uploads/21750/Pond_13-Aug_02.jpg" rel="nofollow">

Did a fair bit of work re-profiling the top lip. I found it needed to be sloped more so that a minimum of the clay was exposed to the sun (else it dries and cracks). It will help newts get in and out more easily too. Smile

That's it for the pond (I hope!) plenty of work still to do to tidy up the surroundings (including the 5 foot high pile of spoils from the pond I was standing on to take the pictures) but apart from that and adding some plants, it's up to nature now. 

Posted By: will
Date Posted: 13 Aug 2014 at 6:31pm
terrific work for sure, Gemma.  I'm sure it will be appreciated by the local amphibians - and then maybe the grass snakes...

Posted By: GemmaJF
Date Posted: 13 Aug 2014 at 6:50pm
Can't wait Will! Today it was really nice just to have water back in the garden, things feel right again. I've really missed the dragonflies and damselflies too, excellent for scaring friends and family LOL

Posted By: Iowarth
Date Posted: 13 Aug 2014 at 8:11pm
Nearly 3 years since you first "announced" the project on here. But the wait has been well worth it for us and I am sure all the work has been well worth it for you!

Well done Gemma (and helpers!) - it's looking good. I hope the natural wioldlife wastes no time colonising it!


Chris Davis, Site Administrator

Co-ordinator, Sand Lizard Captive Breeding Programme (RETIRED)

Posted By: Tom Omlette
Date Posted: 13 Aug 2014 at 11:29pm
looks bloody awesome gemma well done Thumbs Up

Posted By: Paul Ford
Date Posted: 14 Aug 2014 at 8:17am
Very impressive Thumbs Up

Posted By: GemmaJF
Date Posted: 14 Aug 2014 at 9:42am
Thanks guys, the water is beginning to clear now. Overnight the water level dropped a few inches, but I can clearly see the culprit is a breach in the clay liner. This is where I re-profiled the top edge yesterday and took a bit too much out. As might be expected, the breach is in the most inaccessible side, so I'll be sitting in the nettles on the side of the bund this afternoon patching it over! This seems to me the big advantage of the clay compared to concrete and plastic liners I've used in the past, it's so much easier to fix if there is a problem.

This morning the garden is full of birds, the local flock of sparrows we call the 'Squadron' visited and all the young lined up around the edge of the pond to drink whilst the parents watched over them. I think Suz coined the line 'just add water' to bring life to a garden, how true that is! Smile

Posted By: Suzy
Date Posted: 14 Aug 2014 at 1:59pm
Ponds - always something interesting. Yesterday I was sat reading by my newish large pond when a male banded agrion damselfly landed momentarily nearby. Never seen one of those here before.


Posted By: GemmaJF
Date Posted: 14 Aug 2014 at 4:20pm
I use to see banded agrion, though I think we called them demoiselles, when walking along river Stour in Suffolk, not seen any locally though. Beautiful creatures to watch in flight. Don't know if Keith sees these along the Stour in Sudbury?

Most likely fist dragonfly to use our new pond will be Broad-bodied Chasers, they seem to be particularly attracted to new ponds, and also happen to be one of my favourites to watch. Smile

Got back from shopping this morning to start work on finishing the pond, and soon after the sky went very black and the heavens opened. Did though manage to clear the bund a bit before the rain, so at least the job of fixing the pond will be a bit more comfortable now (I won't have to sit in nettles and dried brambles!). The bit I have cleared used to be a favoured basking spot for grass snakes, so they'll probably appreciate it being a bit more open again now too.

Posted By: GemmaJF
Date Posted: 20 Aug 2014 at 10:41am
A quick update on the pond.

We've found we are still losing about an inch of water overnight after repairing any obvious damage.

I've done more research and though the mixing subsoil method we used is often recommended I have my doubts about it. It is very easy to say miss a patch a few inches in area or end up with very thin coverage in places. Particularly it's very easy to pick up a patch of the liner on the bottom of a welly when walking about on it!

I've found a different method called the 'blanket' method. Here a relatively thick layer of the Bentonite is applied as a single application. Then soil is added over this and compacted. The big advantage is it is self-sealing. If the clay liner is punctured there is a whole layer of partially reacted bentonite ready to expand and fill the hole. It reminds me the way self sealing fuel tanks worked in WW II.

I've ordered an entire ton (40 bags) of bentonite to apply a new blanket layer to the pond.

At this stage I'm looking at it as the glass is half full (pond???), as we now have a perfect shell to apply the blanket layer to and have a well established top edge. The only problem right now is we need to keep topping up so the existing clay doesn't crack in the sun!

I've got some plants now too, I'll do a full list when I plant them up. I collected a couple of specimens of very common plants from a favourite childhood pond and also ordered white water lilies and a Frog & Tadpole pick and mix from here:" rel="nofollow -

Just got to wait for my ton of Bentonite to arrive Smile

Posted By: Suzy
Date Posted: 20 Aug 2014 at 12:18pm
What a bgr Gemma! So you will  have to siphon out the water, I guess. Good luck with it all, enjoying reading your progress.
Incidentally has any wildlife moved in already?


Posted By: GemmaJF
Date Posted: 20 Aug 2014 at 1:26pm
We'll hire a submersible pump to get the water out Suz, it was pretty impressive last time and shouldn't be too much hassle to do. 

Starting to see dragonflies about we also have some tiny water beetles swimming around already

It is only taking a ridiculously small trickle of water to keep it topped up, but as we all know it only takes a tiny leak for a pond to lose a lot of water in a day!

Posted By: Suzy
Date Posted: 20 Aug 2014 at 3:07pm
Absolutely best to get it sorted at the start. Ah a pump, makes it easy.
Funny isn't is that dragonflies like new ponds and then desert them as they get established.


Posted By: GemmaJF
Date Posted: 21 Aug 2014 at 9:07am
Absolutely Suz, better fixed at the start, would hate to have to top it up all winter and let wildlife get established, only to have to drain it all next year. We are in good shape though as we still have a large spoil heap available to coat the new  bentonite blanket layer, so in all not too inconvenient. 

Yep it is interesting about dragonflies, when we first put in the pond 10 years ago the first and second year we had dozens of them, then it died down a lot as the plants got established. Seems counter intuitive as many species deposits their eggs on leaves. Confused

Posted By: GemmaJF
Date Posted: 07 Sep 2014 at 3:59pm
Update pictures to follow soon!

There has been plenty of work going on to redo the pond. I'm much more confident about it all now after days of back breaking work. I had the feeling it was all too easy the fist time around. LOL

I've opted to fit a semi-liner of horticultural sheeting around the top edge of the pond. Two reasons, one earthworms which were breaking through the clay before and also capillary leaching into the top soil. I think both were factors in the pond level dropping all the time.

The semi-liner has been covered in a layer of reworked clay. I'm just waiting for it to dry out a bit for final shaping and compacting. Then I'll put in the bentonite blanket layer and top off with a final layer of clay. Easy to say, but it takes a bit longer to do!

Posted By: GemmaJF
Date Posted: 16 Sep 2014 at 9:27am
The clay pond version 2! There was a lot more of what seemed liked traditional clay pond building this time round, the bentonite being reserved as a back-up sandwich layer between compacted clay.

Started out putting in a semi-liner of horticultural sheeting, the main purpose was to stop worms, though it will help prevent any leaching of the water into the sub-soil via capillary action (one hopes!)

The sheet was then covered in an inch of clay:

uploads/21750/Pond_09_September.jpg" rel="nofollow">

The bentonite blanket layer went in next:

uploads/21750/Pond_11_September.jpg" rel="nofollow">

There was a 2 day delay during this process when one entire side collapsed when the liner got dragged down under the weight of the bentonite. I was putting in the last few spade fulls and admiring the moon rise, when huge cracks started to appear and the side of my construction slipped into the bottom of the pond. Not one of my finest moments LOL This picture is after the repair work and the final application of bentonite.

The bentonite layer was then covered with another inch of clay. I found the first time that the bentonite  had a habit of dissolving out and becoming sludge, so trapping it between two layers of clay seemed the way to go:

uploads/21750/Pond_14_September.jpg" rel="nofollow">

As can be seen above there were plenty of late nights! Here the inner clay layer is complete and the pond is finally being filled. I put my plants in as I worked on building the inner layer, this seemed the best option to avoid disturbing it too much.

uploads/21750/Pond_15_September.jpg" rel="nofollow">

Filled up again and the top edge of the clay covered in top soil to prevent cracking. Fingers crossed this time it will all be OK. It's held it's level well overnight with no significant drop, so I'm hoping this time it will work out.

Posted By: GemmaJF
Date Posted: 16 Sep 2014 at 9:30am
Plant list:

White water lily

Brook Lime

Water Violet

Yellow Flag Iris

Fringe Lilly

Marsh Marigold

Water Mint

Water For Get Me Not

Posted By: PondDragon
Date Posted: 16 Sep 2014 at 4:08pm
The pond is looking pretty good - you seem to have put a huge amount of effort into this project. I'm puzzled though that you want to plant White Waterlily and Yellow Flag - both monstrous plants that are likely to take over. Potamogeton natans, Hippuris vulgaris and Eleocharis palustris would be good alternatives. The Potamogeton is quite vigorous, but there are lot of insects that eat their way through it. The other two are both quite 'open', so you can get a nice mix of shallow water vegetation with other species growing amongst them.

Posted By: GemmaJF
Date Posted: 16 Sep 2014 at 4:33pm
I chose yellow flag and white water lily because I like them! I had both in the previous incarnation of the pond built over a decade ago. Both have their roots contained, though I appreciate both can be problematic I'm hoping I can keep them under control! They also remind me of a favourite childhood place, so they  were a bit of a must have. 

I appreciate you taking the time to list some alternatives, I have plenty of room left for more plants so will give them consideration. 

Though have to own up to finding mare's tail an extremely odd looking plant which I can never decide if I actually like or not! Always like seeing it when out and about but not so sure I would want it in the garden pond.

Posted By: PondDragon
Date Posted: 16 Sep 2014 at 6:52pm
I agree that they're both attractive plants, and very good in the right place. But they do leave quite a bit to be desired in a wildlife-oriented garden pond. The larger waterlilies have a tendency to grow so densely that submerged plants are shaded out and a substantial % of the pond area ends up pretty lifeless. Looking at the Potamogeton natans in my own garden pond, it's spread vigorously in area this year but not to the total exclusion of everything else (the leaves are relatively thin, widely spaced, short-lived and liable to being eaten by e.g. Donacia versicolorea and China Mark Moth), so there are still submerged plants underneath it (mainly Bladderwort, Hornwort and Potamogeton berchtoldii/pusillus).

I don't know how well restricting the roots will work in practice - I suspect you may have to choose between a well-fed, vigorous, flowering plant, and a starved, small, poorly flowering one.

As an additional suggestion, one or two large, craggy pieces of semi-submerged deadwood can look good and are very popular with birds and dragonflies. Obviously that's getting ahead a bit - hopefully your clay liner works and it continues to hold water.

Posted By: Suzy
Date Posted: 16 Sep 2014 at 10:33pm
I have two types of pondweed and they don't take over, as you say they get eaten or decay. Attractive flowers too. I had starwort and loved it but it got smothered and killed by the dreaded duckweed. The latter appeared when brooklime completely carpeted the pond and somehow the duckweed snuck in underneath and thrived in the shade created. I've never been rid of it since!
I am surprised you suggest mare's tail. A very invasive hard to eradicate weed.
Frogbit is a nice plant with delicate flowers at times. Love the small round leaves.
I would have water lilies if I had a big pond.
I have water forget me not in both my ponds but it spends a lot of time looking fairly drab.
Pond is looking good Gemma - good luck!


Posted By: Tom Omlette
Date Posted: 16 Sep 2014 at 11:14pm
looking great gemma. i'm knackered just thinking about the hard work involved!!!


Posted By: GemmaJF
Date Posted: 17 Sep 2014 at 8:21am
Originally posted by Tom Omlette Tom Omlette wrote:

looking great gemma. i'm knackered just thinking about the hard work involved!!!


I'm still exhausted several days after finishing it!

Starwort is a favourite of mine too Suz, not sure how it managed not to be on my list, have to get some. I've always thought it was pretty ideal for small newts to lay eggs on.

Posted By: GemmaJF
Date Posted: 17 Sep 2014 at 8:39am
Originally posted by PondDragon PondDragon wrote:

I don't know how well restricting the roots will work in practice - I suspect you may have to choose between a well-fed, vigorous, flowering plant, and a starved, small, poorly flowering one.

Perhaps for me that is the point, both plants are natives and will cause problems if fed large quantities of nutrients. In many of the situations where I see them in the wild nutrients are limited and they are not troublesome. In all I try to keep nutrient levels extremely low in wildlife ponds. Some of the best amphibian ponds I know of have barely any aquatic vegetation. Many others I have surveyed would be fantastic amphibian ponds if it were not for high nutrient levels and the resulting over proliferation of one or two plant species that results.

Posted By: PondDragon
Date Posted: 17 Sep 2014 at 9:45am
Originally posted by Suzy Suzy wrote:

I am surprised you suggest mare's tail. A very invasive hard to eradicate weed.

I was referring to the aquatic flowering plant Hippuris vulgaris, not the garden weed Equisetum arvense (horsetail).

Posted By: Suzy
Date Posted: 17 Sep 2014 at 11:18am
Apologies for mixing up my mare's tails. I know the garden weed by that name as well. I had quickly Googled it before posting but the images I saw looked like the garden weed. Am I correct though that the pond variety can also be quite invasive?


Posted By: PondDragon
Date Posted: 17 Sep 2014 at 11:52am
I've never heard Hippuris referred to as being particularly troublesome. It's rhizomatous so it does spread, but the growth isn't particularly dense. I like the way it intermingles with some of the other species I mentioned above - I could try to post a photo later.

Posted By: GemmaJF
Date Posted: 17 Sep 2014 at 7:55pm
I would imagine Mare's Tail in a clay pond could be a major problem though PondDragon? Surely it would happily root in the clay and rapidly take over the entire pond? As the only real option to eradicate it would be chemical I think I'll steer well clear of it!

Posted By: PondDragon
Date Posted: 17 Sep 2014 at 10:47pm
I don't know, but I can't really imagine it being a problem. Apart from anything else I think it does provide good habitat - both submerged and aerial forms. Obviously if you don't like it then don't plant it. Water Mint, now, that is pretty vigorous - sending out long stolons across the pond. Very nice though, and the GC newts love it.

Posted By: GemmaJF
Date Posted: 18 Sep 2014 at 9:18am
Yep one has to keep on eye on water mint, though I could live with a pond full of it!

Posted By: GemmaJF
Date Posted: 18 Sep 2014 at 11:45am
Did quite a bit of tidying up yesterday around the pond. During the re-construction the edge managed to grow up out of the ground several inches as the liner was covered and the other layers added so I'm ding a lot of filling in before trimming away the excess plastic liner.

I've ordered in a couple of large bags of topsoil to help level the surrounding ground.

Water level is stable, I'm keeping it an inch or so low at the moment whilst the top soil settles in an attempt to prevent it all washing into the pond and exposing the clay. 

I've noticed a couple of  places where worms have been active. It is most likely they were in the clay mix rather than they are working their way in from outside the plastic liner. Before the worm holes were clearly visible. Now one just sees a small patch of bentonite as it swells and fills the hole. 

I've improved access all round the pond by digging away a bit at the existing bund too. Finally starting to believe the whole project is now a success! Smile

Posted By: Chris Monk
Date Posted: 19 Sep 2014 at 11:29pm
As Pond dragon hasn't found his photo yet, here's a picture of Hippuris vulgaris dominating the aquatic flora of a pond taken in late April this year.

Three things about this pond
1) It's a great crested newt breeding pond on a SSSI and SAC
2) I first went there and found GCN in 1985
3) The pond looks almost the same as it did in 1985, the marestail has kept the Typha (which you can see scattered across the pond) in check all this time as that was also present in 1985, there is Potamogeton natans inbetween the stems, the water has always been very clear on every visit and it is wonderful for invertebrates as well as newts.

Still not the first plant I would think of putting in a garden pond.


Derbyshire Amphibian & Reptile Group

Posted By: PondDragon
Date Posted: 19 Sep 2014 at 11:41pm
Interesting photo, Chris. I'll try to take some photos of the garden pond tomorrow and start a new thread. An image search for 'Hippuris vulgaris' does throw up various photos of ponds quite dense with it, so clearly it is quite capable of taking over (although, so are a great many other aquatics, including many of those commonly planted).

Posted By: GemmaJF
Date Posted: 20 Sep 2014 at 9:04am
I think one significant factor with a home pond is we can manage it often. I'm keen on heavy vegetation bashes in late autumn to break the nutrient cycle and keep a pond held back in the early stages of succession. Not adverse to a complete clear out every five years or so if needed. 

The problem I imagine with Mare's tail is it would root very quickly in my clay liner and be almost impossible to manage in an effective way. I've come across a post on another forums where someone was asking how to eradicate it from a clay pond which it has taken over. Apparently it's easy enough to pull the stem out, but the root is always left behind. I usually find with stuff like water mint it is fairly easy to get a lot of it out, root and all, making it relatively easy to manage it.

Thanks for posting the picture Chris and looking forward to your pictures PondDragon.

Posted By: GemmaJF
Date Posted: 20 Sep 2014 at 10:03am
Ordered some Purple loosestrife this morning, plan is to put in a boggy bit where the pond drains which should be a good spot for it. More pictures of the pond next week, waiting for my topsoil to arrive so I can finish the surrounding areas and make the wildlife garden look a little less like a building site!

Posted By: Chris Monk
Date Posted: 20 Sep 2014 at 4:49pm
I am sure you are right Gemma that if Marestail became established in your pond you would only be able to pull off the stems and the rhizome would remain in the clay sending up new growth.

I always think that a few purple loosestrife plants look good around a pond - but only in this country. In America it's their equivalent of Himalayan Balsam in that it is invading wetlands and forming dense stands that shade out and prevent germination of the native species.


Derbyshire Amphibian & Reptile Group

Posted By: GemmaJF
Date Posted: 21 Sep 2014 at 8:40am
I read recently about the trouble in the States with Purple loosestrife it seems it is a real menace over there. 

Posted By: Suzy
Date Posted: 21 Sep 2014 at 9:32pm
I have purple loosestrife and it self seeds mildly - not a problem for me. Mine are next to the pond, not in it, so possibly plants with their feet in water really get going.
I do remember it from my Lake District fishing days as a kid. It grew along the banks of a few rivers, but not in great abundance. So it holds happy memories for me.


Posted By: GemmaJF
Date Posted: 22 Sep 2014 at 9:11am
Same as my memories of it Suz, I often find single plants around gravel pits or just small stands in the wild, certainly a lot or my childhood memories are being condensed into my pond planting scheme Smile

Posted By: GemmaJF
Date Posted: 29 Sep 2014 at 5:17pm
Was going to take some pictures of the pond today but it was so gloomy I thought I would leave it until the sun comes out. 

The pond has been in the grips of the predictable algal bloom thanks to being initially filled with tap water and nutrients from the necessary top soil seeping in, add the sunny weather and a perfect recipe for algae trouble.

It's calming down now though and a little less pea green and frothy! I've been gently removing any floating organic material today whilst trying hard to not stir up the bottom so with any luck the algal bloom will be short lived and the pond will find a natural balance as the bacteria get going. Water level is keeping up well so from now on it is top ups from rainwater butts only which should help the situation. 

Species spotted so far, lesser and greater water boatman, they were first to arrive and I suspect were around before the second rebuild of the pond. Spotted a whirligig beetle the other day and also plenty of gnat larvae. Watched a common darter pair busy egg laying too, so should have plenty of mini dragonfly larva next year. Strangely no pond skaters though which I expected to be quick to arrive. We have water stick insects locally too so will be keeping an eye out for them as they are one of my favourite pond mini-beasts.

Water still needs to clear a bit so I'm hoping there will be more to be found when it does. Some of the plants have also managed a bit of growth in the warm weather with the water mint and brook lime already above the surface and looking healthy.

Posted By: GemmaJF
Date Posted: 30 Sep 2014 at 9:21am
Sun is out this morning so some pictures!

Green hose pipe is from our medium sized water butt fed by the shed roof, yellow one is supplied by a big butt that collects the rain water from our garage roof.

Grass is coming up around the edge of the pond, this is a small bog garden adjacent to the pond planted with purple loosestrife plugs.

Larger bog garden, also has some purple loosestrife, but I'm planning on more extensive planting in the spring. The cat scarer tends to drip a bit and also wet the ground around it when activated, so it makes sense to put it in the bog garden to keep it wet. It's usually connected to the yellow hose pipe to the mains water supply.

View, looking towards my extensive goth pumpkin field LOL Not long to All Hallow's Eve Wink

Bird table is bare because the adjacent arch has just been painted, I don't want the birds to get paint on their feet!

New stepping stones, hopefully it won't be such a battle through wet clay on New Year's Eve this year to get to the pond and photograph newts!

I think that's job done now in the wildlife garden other than putting in a hawthorn hedge right at the back. To the right of the stepping stones I'm planning extensive decking, to the left is my veggie plot, carrots and parsnips shown above are very tasty Smile

Posted By: will
Date Posted: 30 Sep 2014 at 10:49am
great effort Gemma, I'm very jealous (and too lazy to even contemplate doing anything so industrious myself)..

Posted By: GemmaJF
Date Posted: 30 Sep 2014 at 12:34pm
Thanks Will, generally I would be too lazy to do it also and was for several years, but I injured my back and doing stuff in the garden (and avoiding sitting down for anything other than short periods) has really been the best therapy for it possible. I'm almost afraid to stop in case the back and leg pains come back. At the start of the year it was a struggle to walk to the pond I was in so much pain and thoughts of renovating it seemed pretty fanciful.

Some fauna and flora pics from today:

Whirligig making ripples around the now emerged Water Mint

Greater Water Boatman

Brook Lime is up and away!

Also caught sight of a diving beetle, probably Common Black Diving Beetle but didn't get a good look (or a piccy) before it disappeared into the still rather murky water.

Posted By: Suzy
Date Posted: 30 Sep 2014 at 12:48pm
Looking good Gemma. Well done!


Posted By: will
Date Posted: 30 Sep 2014 at 4:15pm
Glad to hear it was good therapy Gemma; digging my current pond literally gave me a hernia - and the b*gger is in the wrong place anyway!LOL

Posted By: GemmaJF
Date Posted: 30 Sep 2014 at 6:23pm
Sounds painful Will, probably best to just leave it in the wrong place Wink

Posted By: GemmaJF
Date Posted: 02 Oct 2014 at 9:26am
I was going to wait until the spring to plant up the bog garden, but it looks so empty I succumbed this morning and ordered, bog bean, bog arum and Branched Bur-reed. 

I know Bog arum isn't a native, but it is naturalised locally and was growing naturally in the wildlife garden before I turned it into a building site whilst renovating the pond. Sadly it was situated where the new hedge is going to be and is unlikely to survive, so it seemed only right to buy some to plant in the bog garden.

Ordered again from Puddleplants ( who have provided an excellent service and quality of plants, would thoroughly recommend them. You sometimes get an extra one or two plants in the order too which I find a lovely touch in this day and age. Clap

Posted By: GemmaJF
Date Posted: 03 Oct 2014 at 4:10pm
Plants arrived for the bog garden today:

Posted By: Tom Omlette
Date Posted: 03 Oct 2014 at 10:19pm
great stuff gemma. love the pics. keep 'em coming :)


Posted By: GemmaJF
Date Posted: 07 Oct 2014 at 11:26am
Pond is full to the brim after rain Saturday and early this morning:

Grass is pushing up nicely, still very murky in there though!

Not sure of the species but we have a lot of little beetles that have appeared. They float on the surface along with the gnat larvae and dive down when disturbed. They are black and about 2 mm long.

Posted By: GemmaJF
Date Posted: 08 Oct 2014 at 10:08am
Pond is overflowing this morning with more heavy rain overnight and this morning! Thought it best to leave it in overflow and see if that helps to reduce the nitrogen level after the initial fill with tap-water. I'm so excited about what spring will bring to the pond, I could almost burst Big smile

Posted By: Suzy
Date Posted: 08 Oct 2014 at 10:49pm
Imagine that day Gemma as you approach the pond and something swirls off...frog...newt...or you go out one morning and there is a clump of spawn, or maybe several! I think it is the sheer unpredictability of what might turn up that is so exciting. 


Posted By: GemmaJF
Date Posted: 11 Nov 2014 at 7:31pm
Been away for a couple of weeks due to no internet access. Somebody knocked down the telegraph pole in the village that carried our line apparently!

Observed this on the 28th October, seen a newt in the same place several times since using the infra-red night camera, including tonight at around 19:20

Look at the edge of the pond at the bottom and approximately in the middle!

So the first amphibian spotted using the renovated pond Smile

Posted By: Iowarth
Date Posted: 12 Nov 2014 at 8:24am
Well done Gemma.

Video refused to load until this morning and I am definitely bleary eyed in the mornings, but nevertheless saw the bottom left newt very clearly.

All the best

Chris Davis, Site Administrator

Co-ordinator, Sand Lizard Captive Breeding Programme (RETIRED)

Posted By: Suzy
Date Posted: 12 Nov 2014 at 11:14am
Brill Gemma. Sadly with all my duckweed in the smaller pond I wouldn't see anything.


Posted By: Clem
Date Posted: 03 Dec 2014 at 11:05pm
Hi there All,

May I say what a great project! Congrats. I've read the whole thing with great interest as I shall be building a pond on 13/dec/2014 with a team of friends, about ten of us.

My idea was to have a clay bottom only. We are a permaculture group of a natural non-toxic sustainable material and process is paramount. Given the labour available I am hoping to have three layers of clay of about 6-7 cm each using the local soil as it is very high in clay content.

My main question is about the worms. Living in Cyprus we do not have many worms here but hopefully with the permaculture project under way I'm hoping that there will be more and more in the field. I see mentioned soot and lime. What about fire wood ash, would that work? (is good against snails and slugs). And I presume that the worm repellent would be placed underneath the clay.

What about the top soil? Is that for aquatic plants to use, and is therefore placed on top of the clay, or is it for "external to the pond" plants, and therefore placed under the clay?

We shall be building a rain water harvesting system on the 1.5 hectar field with drains and swales, overflowing into the pond. Planting shadowing trees around the pond to prevent evaporation. Is a weeping willow acceptable or is it too water thirsty and may jeopardise the pond clay structure? Also hoping to have some fish in there but that will be after a Cypriot summer and see if the pond holds.

Also, how does the top lip of the pond works? We don't want the clay exposed to the sun but we don't want top soil leaching into the pond either. Would of dwarf stone wall on the clay be a good hedge between the two? Holding back top soil and shadowing the clay.

Any advice in this project is very welcome and appreciated. Thanks!

Posted By: GemmaJF
Date Posted: 04 Dec 2014 at 10:26am
Hi Clem,

The soot would go under the clay to stop worms. I have found it very effective to use PVC plastic as a barrier for worms though and this also prevents water leaching into the top soil via capillary action in hot weather. I think wood ash may work, though may be very acidic and would not give the protection against water loss due to capillary action.

The top lip I formed in clay, then covered with the top soil. This in retrospect was probably a mistake, it would have been better to cover it with sub-soil so less nutrients were able to leach into the water. Though in my own situation the sub-soil was.... ....clay! So it really didn't occur to me at the time. If a non-clay sub-soil is available, this would be the best solution for covering the top clay lip. Some top soil went into the pond for aquatic plants, but most of the 'in the water' soil is in containers. Mainly I have done this for ease of maintenance. I have built plenty of healthy wildlife ponds with a lot of top soil added, it just takes time for a balance of bacteria to build up and control the algae which will at first dominate and plants to establish that draw nutrients out of the water.

It is very important the pond is always kept topped-up to prevent  bare clay being exposed to the sun.

I think stone or large pebbles could be a good solution to help protect the clay, my pond has yet to see its first summer, though I have this in mind for the north edge which will catch the most sun if it turns out that it is prone to drying and cracking.

Posted By: TheHabitatGardener
Date Posted: 17 Feb 2020 at 7:31am
Hello Gemma and co
Hope it’s ok to post on this old thread. I am now back in the UK (Essex) and planning to build my own garden newt pond... I was wondering how the amazing wildlife pond you created back in 2014 has fared over the years Gemma and if you were to do it all again would you still go for the puddling clay or whether you’d go for a liner?
Many thanks

Posted By: GemmaJF
Date Posted: 18 Feb 2020 at 1:59am
Hi Jilly,

The pond did really well up to last year. Unfortunately an attempt to clear out weed compromised the pond and it is not now holding water very well.

In all I think the better option rather than only puddling might be to incorporate a geosynthetic liner. The plan for this year is to remove the layer of puddled clay, install the geosynthetic liner and then put in the old puddled clay over the liner, to give a natural look again. 

The liners I have been looking at contains a layer of the same sort of bentonite clay I used originally. The advantage is that the geosynthetic liner should make the pond more durable by ensuring there is always a continuous layer of betonite to seal the pond stuck between a plastic membrane.

Link to the geosythetic liner I have been looking at:" rel="nofollow -

So I should end up with a pond that still has all the appeal of the clay pond we originally built, but with the added peace of mind of modern materials.

Posted By: TheHabitatGardener
Date Posted: 21 Feb 2020 at 8:26pm
I’m so glad I asked as I have never heard of this new material and it sounds ideal. It also sounds pricey so I will start saving up! Do you keep yours topped up with a water butt or hose? I have an old bore hole I would like to get working again to top it up in the summer from a clean water source - fingers crossed! Will keep you posted of any progress. Thanks Gemma.

Posted By: GemmaJF
Date Posted: 22 Feb 2020 at 12:15am
I keep it topped up with hose pipes connected to several water butts. Looking forward to hearing about the progress, no doubt it will involve a lot of hard work, but the rewards are always fantastic when creating a new pond.

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