Pond design

geoffs1953 · August 2023

I created a pond last year about 4m in diameter and 1m deep in the middle although a lot of the pond (80%) is shallower between 20cm and 40cm. I have a lot of blanketweed which is now reducing with treatment (barley straw treatment, snails). I have a pump circualting water but many of the plants I have intrduced have not survived.

Water lillies in the deepest part are flowering well although the leaves look a bit sad but others (iris, horsetail) have not. Oxygenators are all in the deepest part and migrate there if placed higher. There are no fish but plenty of insects enjoying the water.

The temperature of the water is at 28degrees is this too high?

I am considering to expose the pond to dig it deeper in the shallow parts to increase the volume and reduce the temperature. Another possibility is to create some shade by planting a tree on the south side. But this will partly obscure the view of the valley which we are trying to maintain to a maximum. It is the main challenge for our garden.

The goal of the pond is primarily for wildlife. My plan is to introduce a small cascade using the circulating pump. Is this a good idea?

What are your views? Did deeper or not? Shade or not? Pump or not?

Fairygirl · August 2023

Whereabouts are you if the water's that temperature? No idea what mine is, and it's a smaller pond than yours, and much shallower, but the very shallow edges get quite warm in the sun. It doesn't make any difference to the plants though. I have Equisetums, water Forget me nots, water hawthorn, cotton grass, a miniature water lily and the twisted rush all in there, and something else I can never remember the name of. All of them perform well.

Most wildlife ponds don't have pumps. Water lilies don't usually like constantly moving water too near them so you'd have to bear that in mind if you want a cascade or similar.
Have you got a photo of the site?

geoffs1953 · August 2023

I need to work out how to attach photos. I attached two to this mail but neither seems to be appearing. I saw in passing a thread on this topic so will return to it.

The pump is sat right next to the water lillies but the "cascade" entry point is away from the leaves. Not sure which is most important.

I need to go out now so will re-try sending a photo later,

Fairygirl · August 2023

Keep the photos at around 1MB or less and they load better. The icon that looks like hills is the one for photos

Lyn · August 2023

If you’re using a phone for photos try taking them in the landscape format rather than portrait then click on the icon that looks like a little mountain range. Highlighted in photo here,

if it won’t load from that, you will have to reduce it a bit. Try just chopping the edges off.

geoffs1953 · August 2023

OK, it seems the problem was the file size. Both now reduced to around 1M so hope they are clear.

The first one shows the profile of the pool as the liner is placed. The edge depth is about 15cm, the next level is around 30-40cm and the deepest is 1m.

The second image was taken this morning showing the water colour and some of the plants (living and dead). I am fairly convinced that it is the water temperature causing the problem with overall low oxygenation due to the blanket weed. This I hope is on the way to getting better with snails and barley straw added.

But I believe that it should be full of vegetation by now. There is in the deepest part with the lilies and plenty of Myriophyllum but elsewhere it is very sparse (even the water hyacinth!). There are 4 lilies each one giving multiple flowers through the summer. So I think that they are OK. It is the ones in shallower water that are not OK.

Your comments are really appreciated.

Image: https://us.v-cdn.net/6030279/uploads/editor/ur/s51oismc0fzf.jpg

Image: https://us.v-cdn.net/6030279/uploads/editor/aj/2cgq5m62gh2y.jpg

Lyn · August 2023

I will be honest and say that those layers are too shallow, if it were mine I would remove the middle layer so as to make the deep bit much bigger. You only need a ledge of about 12” wide even 9” just to stand some pots on. Water lilies grow very big and like deep water so that’s a good reason to extend that bit.
If and when we have a drought, the water will disappear from those shallows. That’s the reason the water is too hot and in the winter it will freeze.
dont worry about blanket weed, once your plants are happy they’ll grow and fill the pond, the blanket weed will disappear.

So, if you are able to dig it out, get rid of the middle shelf altogether and narrow down the outside edge, it will be lovely.

geoffs1953 · August 2023

thanks Lyn, I think that is the best remedy. I wanted to get some other opinions before embarking on what will be quite a complex project and to be sure that other solutions were not possible.. I became convinced that water temperature is the root cause and that there is too much surface, not deep enough. So I am still interested in views/experiences of the limits for the pond water temperature.

I shall probably be able to do it in the second half of September.

I am originally from Devon, also west of Dartmoor. I love the county but rarely get back there nowadays. I am now south of Brussels and, surprisingly, we also get a lot of wind.

Fairygirl · August 2023

4 water lilies is a lot for that space. Unless they're dwarf ones, and even those get quite big.
I wonder if the plants you're using simply aren't at the right depth. I have quite a few marginal plants [mentioned earlier] so they don't mind being in shallow water, and I only have a small, deep bit which just has a pygmy water lily and the water hawthorn, although it seeds around itself. It's a good plant for cooler, shadier sites though, so it may simply be too hot for it.
My pond isn't very deep - even in the middle. I'd have needed a digger to get through the clay and rubbish in there.
What oxygenators have you used? Watercress chucked in is good for creating some surface shade too, and also helps with blanket weed as it uses up nutrients. You just chuck it in - and it roots and seeds around. Most supermarkets sell it.
I think it'll help once you get planting around it too - that's necessary for wildlife to give them cover.
This is how mine looked in early May.

Image: https://us.v-cdn.net/6030279/uploads/editor/8l/tpb2qrlnmqvn.jpg

This how it looked a few weeks ago

Image: https://us.v-cdn.net/6030279/uploads/editor/qq/6i6kaph0zreb.jpg

geoffs1953 · August 2023

I have not tried watercress, but read that it could be a solution. For the moment I have put in one of the proprietary barley straw treatments in the form of pellets wrapped in old stockings.

The oxygenator is Myriophyllum ( as far as I best recall) but it all stays in the deeper part with the water lilies.

Yes, 4 lilies is perhaps too much - I got greedy! They should have a bit more room if we dig out further. Yet they have flowered really well through the summer even if the leaves are now looking a bit tired.

A further complication is that it was filled (and topped up) with tap water. However, I have now just installed a pump to take rainwater from an underground cistern so recent top ups have been from there which should also help.

At least it will help with the water but not the temperature. Do you know to what temperature the water gets to in your pond? It looks very shallow.

The planting at the pond edge has developed well this year but all will need to be moved temporarily if I dig it out further. I left a large area of liner outside the raised edge and when the pond overflows it keeps the area damp. In the rework, I am think to reduce the height of the pond edge so that the area becomes a part of the pond filled with soil.

Thanks for your comments, I like your use of gravel in the garden with the pond.

Fairygirl · August 2023

Your oxygenators have to be appropriate to the volume of water, but it's also a question of time with them - as with all plants. They'll all take a while to settle and grow.

You'll need a lot of room for the water lilies if they're larger ones. The big ones can easily spread to 10 or 12 feet or more, but they also need depth as they grow. Mine is around 3 feet in spread, and it's a pygmy one. As they mature, they need lowered, because you need the foliage sitting on the surface, so they usually have to be placed higher up initially. In really big ponds they have to just get on with it and sort themselves out as they grow, unless you have waders...
Tap water is fine if you're in a soft water area - which I am, but if you're collecting rainwater, that's better if you don't have decent rainfall to top up. You can even just fill some containers with tap water and leave it for a few days and that should be ok.
I have quite a lot of very shallow areas - round about two thirds of the edge is only about an inch or two. That's perfect for wasps and bees etc, to drink safely, and the small birds enjoy bathing there as it's very safe for them too. One 'side' has a ledge which is suited to marginals - around 4 to 6 inches, and then the deeper section is around 18 inches depth, and about two or three feet in diameter. As I said, it would have been difficult for me to dig down any deeper, as we have solid clay here, and all of that area was hardcore and paving. That pond is only in it's third year, but some of the plants were just moved from the previous, very small one.
I've never used the oxygenator you have - I have the old one- Elodea, and also Hornwort. If the elodea gets a bit thuggish, I just pull it out.
Sorry - no idea what temperature the water is, but I'll try and rig up a thermometer if I can find one, and let you know.

Pond design

Posts