Substrate for a natural swimming pond - help!

[SwimmingKatherine]

Hi, I'm a newbie here, everyone's advice looks very expert and I'm desperate for some expert advice!

We are in the UK, and building a natural swimming pond. There is a swimming 'sump' that is 14mx4m and then a 'regeneration' area sloping away on all four sides of the swimming area which in total covers around that same area.

We have lined the pond with EPDM and have 20 tons of washed pea gravel ready to go down on the regeneration zone.

We are planning on using plants only to manage the water quality.

So my question, finally, is - what is the best substrate for the plants, to go under the shingle? I don't want to plant the plants in individual plant tubs as the overall look we want is abundant, wild, growth, ie not really able to see the gravel between the plants. So I think we need something between the liner and the gravel.

Aquatic compost on this scale is stupidly expensive but if it's necessary then we'll go that route. Or would coir work, with a bentomite (clay) layer? Or just go for the clay layer and then poke fertilising 'sticks' under the clay near where the key plants are?

Anyone?

I'm really stuck despite extensive googling and double checking of the (otherwise excellent) book 'How to build a natural swimming pool' by Worfram Kircher and Andreas Thon

Thanks

 

[IPA]

Have you tried David Pagan Butler's YouTube channel? I am not sure of any active members with natural swimming pools, most of the knowledge base here is regarding Garden fish ponds. @Big Lou may know the answer or be able to point you in the right direction.

link to David pagan Butler's channel:
https://www.youtube.com/user/davidpaganbutler/videos

I was able to find many other resources using Google's image search, then navigating to the relevant pages. Good luck with your swimming pond; if I were to ever add a pool I think I would go this route.

maybe the big difference is that with fish turning the water volume is measured in number of times per hour opposed to a natural swimming pond that measures this in number of times per day. Therefore the substrate and how nutrients flow through it are different.

 

[Jhn]

So is the idea to have no pump to circulate the water and just use the plants in the regeneration/bog area as the filter?

I would want some kind of filter system circulating the water i.e. a large skimmer to collect leaves and help keep detritus from settling in the deep part of the pond.

I would plant directly in the pea gravel. You can look up addy1's up flow bog design for info.

I guess you could use coir as a medium, ie stringing coir logs in the gravel to get the plants started in, but I would think the pea gravel would work just as well.

We use coir logs occasionally in the building of wetlands. I am not to crazy about it in this application because it degrades. If the plants don't get their root systems into it to help hold it together it will fail eventually, causing the wetlands to start eroding again.

 

[Meyer Jordan]

The plants in the regeneration area of a NSP should be planted directly in the gravel, no pots or other containers and no other substrate.

 

[SwimmingKatherine]

thanks guys, that's so kind of you to respond

IPA I've got the David Pagan Butler video - it was him who set us off on this crazy idea in the first place! He is silent on the subject of substrate.

Jhn that's helpful about Coir, I think I was about to make a very bad mistake there...

and Meyer Jordan thank you, that was exactly the unequivocal advice I was after! Into the gravel (we are using 6mm gravel which I assume is going to be okay - we have 20 tons sitting in our garden so it better be the right stuff!)

So I know what I'm going to be doing tomorrow - shifting gravel!

 

[IPA]

It'd be nice to see your work and the final results if you'll post some pictures for us to enjoy.

 

[SwimmingKatherine]

I'm happy to post some pictures and here are three.

We have one layer of underliner, then 1mm EPDM liner, then another layer of underliner across the regeneration area.

My lovely partner has done everything (with some modest help from me) except lay the liner, which we got experts in to do. - W're struggling with the capping as we don't want to mortar the blocks down on top of the retaining wall (unstable and inflorescence from the mortar will be a problem) so we're having to find a way of holding the capping blocks in place.

Then we will barrel the substrate onto the liner on the regeneration areas, and fill those with plants.

The sump area is now full of water and I went in for the first time yesterday (it was a glorious day here in the UK) and it was Absolutely Freezing.

 

[SwimmingKatherine]

It'd be nice to see your work and the final results if you'll post some pictures for us to enjoy.

have done !

 

[IPA]

have done !

Wow, that's awesome.

 

[combatwombat]

Katherine, how did your NSP turn out? Would love to see some shots of how it looks now.

 

[Lisak1]

Haven't seen here here since August 2017 - in fact, it appears she's not even a member of the forum anymore @combatwombat

 

[loggerhead]

I agree that it doesn't matter the color of the pond liner it will have green grass growing on it in no time that is really slippery. I have EPDM pond liner because of the shape and size of my pool/pond and I love it. I put 20 tons of gravel and ton of aquatic plants I got from creeks rivers and ponds around my area. I started the pool/pond on Oct. 10 2020 and completed it in April 2021 when we started swimming in it. I built everything by myself. The regeneration zone is separated from the pool by a spillway where the pool spills over into the regeneration zone and flows through a ton of plants and the water has been crystal clear from the day I added water. I built the pool as it were a regular swimming pool with pool sidewall jets/ bottom jets and bottom drain. I use a few of the sidewall jets as spray heads I created with PVC pipes to break the water surface and to create decor fountains to break up the water surface and a pressure spray to infuse oxygen into the water depending on how I adjust the direction of flow at any given time. I also created 3 bogs in the natural area with carnivorous plants and other bog plants to help filter the water. I also have a water wheel that spills into the pool area opposite of the regeneration zone and a fountain in the middle of the regeneration zone so everything circulates all around the pool area. The only issue I get is scum on the bottom of the regeneration zone, so I created a PVC vacuum that works off my pool pump and then goes through a sand filter which is the only time I use the sand filter. It takes about 2 hours to vacuum the pond gravel area crystal clear and I have to do this every three moths or so.

 

[loggerhead]

Pics of my NSP

 

[j.w]

@loggerhead
Wow that is a gorgeous set up to say the least!

 

[loggerhead]

Thank you. It was a lot of work, but now it takes care of itself. I use a robot vacuum for the pool and a homemade pond vacuum once ever three months to remove any bottom debris.