February 7th, 2011 by Tim Leave a reply »

We have had the idea of constructing a natural swimming pool for some time now, but finishing some of the other house necessaries have taken preference. However with the deck finally completed and some of the other renovations complete, we decided to tackle the pool next.

Finished pool

Finished pool

This is the third pool we have “self built” and we used much of what we had learnt with the first two in this one. One major difference this time is that we decided that we wanted to build a natural swimming pool. What is a natural swimming pool you might ask? Well my definition is a swimming pool that doesn’t require the addition of any chemicals, relying on natural processes to keep the water clean and clear. If correctly designed, the idea is that pool becomes an extension of the garden and becomes part of your garden’s ecology.

The basic principle of how a natural swimming pool works is, in order to keep the water clear, you need to deprive the algae which is always present in the water of nutrients. This is achieved by the large number of plants and large areas of gravel that the water flows through. The plants and the bacteria that colonise their roots and stones, compete with the algae keeping the nitrate and phosphate levels low. Low levels of these nutrients means the algae simply cannot bloom and the water stays clear.

The idea of natural pools is not particularly new and they do seem to be gaining popularity, however getting reliable and useful information on how to tackle a natural swimming pool turned out to be quite a challenge. Whilst there are quite a number of sites which showcase the projects completed by pool contractors, as well as companies selling bio-filters and related equipment. We found they were very skimpy on details. Some forums do exist which did offer some advice, but generally these were more orientated towards Koi ponds.

This lack of available info is something which I am sure will change as natural swimming pools become more commonplace, especially here in South Africa, although I suspect most experts will probably keep the info close to their chests. A book that did help a bit was “Natural Swimming Pools: A Guide to Building by Michael Littlewood”, however I found it did lack much of the nitty-gritty on how to actually build a pool. So after much reading both along and between the lines here are the basic principles for what I believe will make a successful natural swimming pool:

  • The planted area needs to be about the same surface area as the swimming area (ie. 50 / 50)
  • Swimming area needs to be as deep as possible, at least 1.5m (increases volume of water without increasing area exposed to sunlight)
  • The water needs to circulate slowly but constantly through the system.
  • Total size should be as big as possible (Littlewood refers to a minimum area of 50 sq meters – we broke this rule and opted for an area of 25 sq meters due to space constraints)
  • Water needs to be well oxygenated (plants and/or water action)
  • You need to provide maximum surface area for beneficial bacteria to colonise ie. roots and gravel beds.

Because our garden was not big enough to accommodate a large organically shaped pool and also there is a significant level difference between the floor/deck and garden level, we decided to opt for a more contemporary design.  Here is the final Sketchup drawing showing the planned shape prior to me drawing up the final details. The physical sizes are as follows:

  • Main swimming area : 2.4 m x 4.4 m – depth 2.4m with a continous step along the deck side.
  • Intermediate pond: 1 m x 2.2 m – depth 1.2 m
  • Lower pond : 0.8 m wide x +-10 m long – depth 0.6 m but varies from 0.1 m to about 0.4 m with the gravel inside.
  • Total volume 25 500 litres

Pool Concept

Because we wanted the swimming area to be close to deck level we decided to terrace the pool with the planted sections stepping down to the garden level. This way there was some continuity between the deck / pool level and the grass lower down. One thing we did pick up from other designs was that the water is almost always flows from under the planted area up and towards the deeper swimming area. In our design this wasn’t really possible, but since we couldn’t find any logical reason way it would make a difference reversing the flow, we decided to try it out in reverse.

Digging the hole

The Digging Starts

In terms of physical construction we decided on using standard 190mm wide masonry blocks, reinforced with reinforcing steel and concrete in-fill. The reason for this is we wanted to have narrow as possible walls, and this was the only way I could think of achieving this without going the shuttered reinforced concrete route. To waterproof the structure a glass-fibre reinforced resin system again proved to be a cost-effective solution. Prior to fibre glassing the block-work was simply plastered to the desired shape and detail and allowed to harden.

First course of blocks

First course of blocks

Block work complete

Block work complete

A large part of any natural swimming pool is obviously the water plants and we were  very fortunate that my lovely Mum was easily persuaded to start collecting and cultivating plants. I think she even started collecting before we had started digging the pool. She has very green fingers and very soon had quite a collection of plants happily growing in some temporary containers. Apologies to the neighbours who had to put up with all the mosquitoes who obviously loved the still, stagnant water. It’s interesting to note that there are no mosquitoes in the swimming pool, which I am sure is mainly due to the running water and our collection of eight hungry mosquito fish.

Gravel ready for planting

Gravel ready for planting

Green fingers

Green fingers

In the end she managed to collect quite a variety of indigenous water plants which I believe have contributed largely to the success of the project. We had to create shallow and deeper sections to accommodate the different plant types, but it worked out well in the end as it makes it all the more interesting. Special thanks to Robs & Vaughn who also let us raid their reservoir of additional water plants for the deeper intermediate pond.

In order to get the water to flow through the gravel of the planted area we placed three slotted 40mm pipes running the entire length of the lower pond. These join and then feed into a stainless steel filter box (actually an old dishwasher with a washing machine drum inside). This ensures a steady slow flow of water through the gravel and the plant roots keeping the beneficial bacteria happy and fed, and the water clear. To circulate the water we used a Hailea H9000 submersible pond pump which delivers about 5000 l/h. This means the water is turned over every 5 hours or so but the energy consumption is only 105W.

In terms of costs, because of the additional planted area and the plants, the initial capital outlay is obviously much higher. However in terms of running costs there is obviously no comparison to a conventional pool and there definitely is no comparing the finished product!

Some of the fun things we included was a pool window (at the request of my 8 year old – see ‘Mermaid’ pic below), rainwater top up system with level control and a pool light. The pool has been running for almost 2 months now and apart from one week in the first month when it was pea green, the water has been perfectly clear. Slight variations in colour do occur after rain but are hardly noticeable. Total water consumption (apart from rainwater overflow) has been an average of 150 litres per month, not bad for the height of summer .

For more details and a step-by-step building, watch out for my how-to guide coming soon.



  1. WSM says:

    Your lucid set of instructions has been most helpful, as regards the natural pool. Many thanks. Like you, I found the available websites all fronting commercial installers who stress how difficult it all is to do. Would appreciate some names of the indigenous plants you used, though!

  2. Tim says:

    Actually that’s a good idea – think I will do a post on the plants with some pics and names. I will have to get my Mum to help though since this is primarily her department. So watch this space.

  3. Amanda says:

    Im glad to see that there are others who care about themselves and their impact on the environment. I’m a chronic asthmatic and have tons of allegies and a natural pool has been a dream, Its been years in the making and architects frown when I say I want to build my own natural pool. How did you get the plans aproved?

  4. Tim says:

    Hi Amamda – I simply submitted plans indicating a swimming pool to our local authority for approval – I am not aware of many limitations regards to what you out inside your pool. If you want to fill it with plants and gravel I would imagine that’s up to you.

    I am surprised however that your architects are frowning regards a nutritional pool – doesn’t sound like they very in tune with latest trends ?

  5. Hazel Large says:

    A guy named David Butler built his own pool without using a pump. The planted area is quite big. He has a DVD called ‘DIY Natural Swimming pools.
    If you think about it, what you want is an adapted pond that stays clean and algae free. That was his starting point, and it’s how I plan to build one once I have the property. 🙂
    Thanks for the useful article.

  6. Tim says:

    Hi Hazel

    If your volumes and surface areas are big enough, and you manage to mimic a natural pond shape correctly then natural processes in the water like, gas exchange solar heating will create a natural flow of water between the deeper swimming area and the shallow planted area. Unfortunately this means you need a big garden and it all needs to be on one level. Neither of these were luxuries I could afford so running small pump was an easy trade off.

    The actual running costs are negligible as the pump needed is normally small, mine for example only draws 100W which works out to less than R2.00 or 0.20 dollars a day, so not a big deal.

    Good luck.

  7. Sathya says:

    Hi Tim, I run a retirement village in south india and I had promised the residents a pool. The usage of chlorine has been a major factor in making me interested in swimming ponds. I have the advantage of a higher space availability and plan to have a 12.5 meter by 7 meter swimming / wading space. We are in a place that is dry and warm. Temps upto 34 max in summer. My problem is frogs and tons of them. your elevated pool is quite interesting therefore
    A couple of queries.
    1. I do not want to increase depth to more than 1.2 Metres as most swimmers are old. Will that be an issue as i noticed you recommend depth.

    2. Your filtration system is not quite clear as is the flow pattern of water. Could you help
    Thanks a heap

  8. Tim says:

    Hi Sathya
    To answer your question related to depth, the thinking behind the depth as I understand it is as follows: What we trying to do is control algae which likes nutrients, warm water and sunlight. Therefore if one can deepen the pool (deeper the better) you create a much larger volume of water which will tend to be more thermally stable (think how quickly a shallow puddle heats up in the sun). The other advantage of having deep water, this limits sunlight penetration so the algae needs to compete for sunlight. Its all about giving the plants and the bacteria living in and around their roots an advantage over the algae so they are out-competed for nutrients. If you can think of other ways to control the temperature and sunlight for the the main body maybe you can get away with a shallower pool?

    Regards filtration – this is a bit misleading as whilst the stone bed and plants do do some degree of filtering – primarily they are there to create an environment to absorb nutrients from the water, so the the algae are starved. So the important thing to have, regardless of your system, is a steady, relatively slow flow of water through the stones and the roots. This ensures the bacteria living on the stones and the roots get a steady supply of oxygen and food. This needs to be continuous because the bacteria quickly die with no oxygen and anaerobic bacteria take over – unfortunately these are the guys that create smelly stagnant water smells.

    In my system I achieve this by continually circulating the water – it gets pumped in near the bottom of the main pool, flows over the cascades into the 2 lower ponds. The water is then forced to flow down through the stones and roots because of the slotted pipes at the bottom of the lower pond, which are connected to the pump through the pump chamber.

    A word of caution though – if you can achieve it, it is better to circulate in the opposite direction – ie pump out of the slotted pipes, up though the stones and into the main pond. Reason being the pipes are less likely to clog up with time. Unfortunately this means the planted area must be higher or at the same level as the main body of water – something I could not do with my garden layout.

    Hope that helps – please shout if you need more info. Tim

  9. Hi Tim,

    Congratulations for your pool. It is really awesome!!

    I am writing to you to ask you if you can give us more details about the window. In particular, about the sealant. I am planning to build a pool in my house in the next few months, and I would love to make a window there, but I am not sure about the seals. I will use a acrylic slab for the windows, and a pool will be made from concrete.

    thanks a lot!

  10. Tim says:

    Hi – I used a very ordinary fish tank Silicone, but only because this was the only option I had available to me (most Silicones are toxic to fish life). If you doing a normal pool then your options are much wider.

    Unfortunately I am also not an expert regards the glass – a friend of mine had a sheet of 32mm laminated bullet proof glass about the right size so it didn’t cost me much to try it. I do know depth and size will make a huge difference to the thickness required.

    To make my life easier I welded up a steel frame which I galvanised and built into the wall. We then fibreglassed right over the frame so it had no contact with the water. I then used some black foam strips with adhesive one side, which I stuck to the frame to ensure the glass didn’t touch the frame anywhere. Once the glass was in place I siliconed around the front and back sides – water pressure did the rest! Sorry not sure if this helps much – good luck.

  11. Sean says:

    Hi Tim

    Fantastic looking pool!

    We are in the market to build a pool in Cape Town, and the idea of a natural pool is appealing. However, since they are so rare at the moment, it’s difficult to find details on the building and ongoing maintenance costs.

    What premium is paid in building a natural pool versus a chlorinated pool? Do natural pools really have little ongoing maintenance & running costs? Are there any caveats to consider?

    I’d appreciate any advice you can give.


  12. Tim says:

    Hi Sean

    I have been toying with doing a follow up Blog as the pool turns 1 in a few weeks time, which would answer your questions properly. Unfortunately I am under the usual end of the year rush syndrome so plan to do this next week when things clam down.

    Short answer would be as follows: this is the 3rd pool I’ve built and owned and I will never go back to chemicals purely from an ongoing running/hassel perspective. The pool predominantly looks after itself, I have literally vacuumed the pool twice in 1 year. Apart from this there has just been gardening – ie pruning, thinning and replanting of the water plants, but I see this as an extension of the garden rather than part of the pool.

    So keep an eye out I’ll promise to do a proper update with pictures.


  13. Gary Barnard says:

    How can I get your ” how to Guide”.


  14. Tim says:

    Hi Gary

    I haven’t written it yet – sorry !

  15. stan says:

    Hi, I built a pool with the wetland attached in December 2010. I used one of the companies who does this based in Jo’burg as a consultant and project managed the work myself.Much of what you say i totally agree with and used the same books as you…or tried to !I used the same drainage pipes under 1 m of gravel pumping into the pool with a rim flow back into wetland.
    In the first 6 months mine was almost perfect then suddenly algae arrived .While the water is perfect algae grows on the walls and floor and in the wetland.It is driving me crazy and am even contemplating giving up.The consultant seems to be guessing as we have tried 5 or 6 solutions none of which has helped much.The last was to throw in LAN 28 fertilizer and now my pool is greener than my lawn !! Can you or anyone else suggest anything ? PLEASE

  16. stan says:

    Sean. I am based in Noordhoek and happy to share my experiences.I have seen 4 or 5 pools in Cape Town.

  17. Tim says:

    Hi Stan

    Sorry to hear you having grief – what on earth was the logic behind adding nutrients (LAN) to the pool? LAN is basically added nitrates to the system which is exactly one of the this you trying to remove. Not surprised water is green the algae must think it is Christmas 🙂

    My water has stayed perfectly clear throughout but I have had stringy algae (of various types) come and go in the planted area. It used to stress me out but I have taken a more Zen approach and just let it sort its self out which seems to work. Basically my understanding is that it means there are still too many nutrients in the water, I would imagine you need to either increase the amount of plants or you could install a biological filter. This is basically an oxygen rich environment with lots of places for bacteria to colonise. These bacteria specialise in converting phosphates and nitrates making them unavailable to the algae. The guys that pull this off well are the Koi pond chaps – as they have to deal with all the fish nutrients and excess food they add to the system. They seldom get away without a specific biological filter.

    Just remember though that your planted area is essentially a biological filter where the bacteria do their thing, its just not as specialised as the commercial ones so it should do the job provided it is sized correctly and the water flow and oxygen levels are correct. Not sure if this helps – Tim

  18. Dean says:

    Hi Tim,
    Great to be able to read your article & all the comments as I am also contemplating converting a small pond into a natural pool. I have a property in the Natal Midlands so do you foresee any problems in areas in South Africa with colder climates & where snow is not uncommon?
    There seems to be a lot of pessimists out there so I would love to prove them wrong!

  19. Tim says:

    Hi Dean
    As far as I can establish the big movement for these pools started in Germany were it obviously get as least as cold as you describing – if not colder. The thing to ask yourself is do the local healthy streams and their vegetation handle the cold? So the trick will be to make sure you stick to local indigenous water plants and it should be fine.

    Obviously there would be some precautions protecting the mechanical side / pumps pipes form freezing damage – the plants I am sure will look after themselves.

    I notice that in the very cold parts they winterise their ponds, whereby the turn off the pump completely and let the pond lie dormant – I doubt with the water near freezing much grows so probably not an issue.

    Oh and ignore the pessimists, Tim

  20. Dear Tim and others
    From experience I would like to add: If you have a natural pool without the aid of a mechanical filter such as a pool sand filter, you will need to run the water from the main swimming area over and through the sand (aggregate) bed and throgh the slotted pipes to ensure the removal of debris from the water. As a natural pool in essence want to move away from the consumption of energy (pump) the sand filter is not an option. When working with a bio filter as in a Koi dam, the water must move through the media from the bottom up (through bio media); and as this is not a regenerative zone as in a natural pool, a sand filter is normally added to cope with the extra load on the water. The aggregate bed is both mechanical filter and regenarative zone at the same time, this the reason for its success if sized correctly. We live in a very hot and humid climate (Lowveld) and the size of the regenarative zone may be as high as 1.3 or 1.5 times that of the main swimming area. Plants play a vital role. If your mix is not correct, problems such as algae blooms may arise when more load is put on the system, such as rain, many bathers etc. Imperative is that the plants occur naturally in the environment you are in (indiginous) and that you plant floating plants (lilies) intermediate (1m high reeds,rushes) and high (rushes, reeds) I tend use the flowering varieties as they are not only aesthetically pleasing but also are more robust. The secret of plants are their roots. Not only what they remove or add to the water, but also which animals the attract, both aquatic and non-aquatic, all playing theire part.

  21. bradley says:

    am pondering the option of a nsp and am knowledgable with both water chemistry and swimming pools as i am a traditional pool service man by trade, just have information that may help at startup as the fastest way to get your benificial bacteria in your pool is to start the ammonia process as wich one can do this by dumping raw shrimp maybe a pound intoyour regeneration zone wich will break down into nitrogen in a week thus mixing in a high oxygen environment , i have this knowledge because i used to have a reef aquarium ,

  22. Tim says:

    Wonder if I could ever get my wife to swim after this 🙂

  23. Gavin says:

    Hi Tim,

    Thanks for your valuable info! This was more useful than all the websites I found combined, also becaude they use different terminology for pumps etc and thats where I get confused. Have you gotten round to writing that how to guide yet? If so please mail me a copy! I am starting to build a house in the mountains near Nelspruit, and would like to use as little energy as possible, thus my wanting to build this kind of pool.

    As far as aeration goes, did you install an air pump as a seperate aeration system, or does your normal filtration system aerate the water?

    Thanks man!!


  24. Tim says:

    Hi Gavin

    Thank you for the complementary post, agreed info is hard to come by. Regards aeration I haven’t done any additional aerating save my 2 small waterfalls. I don’t think even this will be necessary if you stick to the min 50 % plants vs swim area (prob 60 % plants vs 40% even better if you have space) and you make sure the water is always moving – ie no dead spots – very NB. Nature is quite capable of doing the oxygen exchange with the air provided you keep it circulating – and don’t overload the system – ie fish !

    If you picking up poor oxygen levels – smelly anaerobic areas (think swamp) or decide to add fish (bad idea in my opinion) – then you can always add it later.

    Regards the guide – alas no I had good intentions but family life and work pre-vales – it is intriguing to know there is a demand though so maybe I still will.

    Please feel free to ask more questions – more than happy to help.

  25. stan says:

    Hi Tim,
    I posted back in january and then went travelling on and off and forgot to check your reply.
    I am still struggling and have probably used 3 or 4 products recommended by the experts but no change.
    I have read many books and web sites so understand the theory very well but the two commercial builders of these pools ,one Joburg and one cape town cannot come up with the answers.One said my wife doesn’t love the pool enough which causes algae !!
    I regularly check the phosphates and nitrates and Ph and all always correct.
    Do have any experience with UV lights or filters as I am at my wit”s end.

  26. Tim says:

    Hi Stan

    My basic understanding is there are two types of algae – the small suspended ones (turn the water green) and the stringy stick together variety (can be floating or stuck on walls in long strings).

    UV filters are good at handling the first type as they floating in the water but the UV also kills all the other critters in the water – so if your water is clear then this this wont help you at all – might even make it worse?

    The second type are a huge pain to get rid of as the only options are mechanical removal or depriving them of nutrients. If it makes you feel better I always have a bit hanging around – but because of my design the swim area is easy enough to keep clear by a quick brush. If it gets too bad amongst the plants then I just scoop it out every couple of weeks. If you think about it they just plants so they might look a bit slimy but at removing them is a good way of removing biomass from your system.

    Have you looked into adding a dedicated bio-filter – this would help as these are suppose to be very good at depriving algae of nutrients ?

    Also have a read though some of the other posts above as some are relevant to your question – sorry I cant help more. Tim

    PS mine is looking really good – just gave the swim area a vacuum so looking forward to some summer swims. Was surprised how little muck there actually was at the bottom after 6 months of total neglect.

  27. johan says:

    Hi Tim,
    As everyone said, much information is not available. I have an existing pool and plan a separate wetland/pond as regeneration area, connected with a short stream to the swimming pool. Small pump connected to the pool weir to skim and pump the water to the waterfall at the beginning of the regeneration pond which is planted and slightly higher than the s/pool. Possible bio-filter after the pump, before the waterfall. No slotted pipes under the gravel in pond.
    Big question – can this work? Thx for the article. Johan

  28. Tim says:

    Hi Johan – yes it can work as it is essentially what I have – but in reverse. Key is to have 50%+ planted area (ie at least same surface area planted as the existing pool – more plants the better!). Other key is to make sure you have good circulation throughout the system with no dead spots – goes for main pool and planted area. This is where the pipes come in handy as it forces the water through he stones keeping the bacteria living on the roots and stones happy. If you think you can still achieve this then it should work just fine. The bio-filter is essentially a concentrated version of the stone bed/roots system but with good circulation so it works well as a booster. Good luck.

  29. Thanx for posting this, loads of info in this one post. A step by step guide will really be super cool, but as always we all suffer from the lack of time. A nice technical drawing/ google sketchup file as the current pool looks like with its pipes, sizes, filter box location would really help I think 🙂

  30. Tim says:

    Hi Coenie

    Time is indeed always a problem – esp if you try do everything yourself + earn a living
    Comment noted about sketch-up though, good idea – just to find the time 🙂
    Thanx for the email.

  31. Jonathan says:

    Hi Tim. Thanks for the trouble you have taken to share your knowledge with us and for the detailed replies to people’s posts. I am in the Cape Town area and planning to build a natural pool of my own. On my previous property I had a fish pond with a small electric pump and the reeds and water plants helped to keep it clean. Also built a biological filter which must have played its part. I used to prefer going for a dip in the pond then swimming in my pool. It was only when I started to plan a large formal swimming pond that I realised other people had the same idea and that there was a whole industry out there. My big concern is the cost of electricity, which is shooting up. Are you still happy with the pump that you are using and the costs attached to it? Have you ever investigated the use of alternative energy sources such as wind, sun, etc. I see some natural pool suppliers offer this as an option. Regards – Jonathan

  32. Brink says:


    Seeing that you still get constant comments on this write-up, maybe you can answer a question I have with regards to a natural swimming pool. I’m only starting to consider this and still needs to do more research so please excuse me if I ask a stupid question.

    I notice from all the info/pictures on the net that all these types of pools have the pool and pond sections next to each other.
    We are considering building a natural pool but want the regeneration pond and swimming pool seperated. Any reason why this should not be done and creating a little “river” and waterfall feeding the water into the swimming pool and pumping the water back into the pond?
    Due to the layour of our property we have more than enough space but it is terraced and will not allow for everything to be done on one level.

  33. Tim says:

    Hi Jonathan

    I am very happy with the running costs as they still in the order of a R100 per month. I have looked in solar and wind but the capital costs are simply not worth it – our electricity is still too cheap! This may change with time but it will take a few years. The real problem is running 24hrs a day as this requires batteries which are expensive.

  34. Tim says:

    Hi Brink
    No reason why this wont work – keeping the water circulated is the key so there are no dead spots in the system – also your energy costs increase as you have to over come the height difference when you pump back – but mine is basically 3 separate ponds with waterfalls so adding a river in between shouldn’t matter.

  35. Anton says:


    I am also busy with a natural pool. Thanks for the website and sharing your advise.
    I have a questions if I may ask. My pool is 4×2.5×1.6=16 and wetland 3×2.5×1.2=9. Together is 25 cubes. What is the standard turn over time? 5 hours? Thats means I need a 5000 l/h pump? Where can I buy a submersible pump. Can’t find any info on the internet.
    My pool in also higher, with overflow into the wetland. Think the overflow creates nice aeration with helps.
    I plan to have maybe more than one flow into the pool to keep the water moving. Your is at the bottom? Which forces water up and over the weir, good idea.



  36. Tim says:

    Hi Anton

    Your calcs seem right – the 5 hours isnt really a standard as far as I could find out – but certainly works for me.

    Have a look at this site its where I got my pump from – I used the H9000 and it is still going strong. (I have no affiliation with them at all but have got good service in the past)

    You may need to go a size up to accommodate a higher lift – just use the pump curves as a guide – obviously each pump will deliver less as it has to pump higher.

    Good luck Tim

  37. Anton says:

    Thanks Tim

    One last thing. What product did you use for waterproofing and are you happy with it. I want to do a decent job with the water proofing, because it can cause a lot of trouble later on.



  38. Tim says:

    Hi Anton – I would recommend fibre-glassing if you going to be building it in brick / concrete / plaster. Horrible job speaking from experience but not difficult – I sub contracted this last time out to a pool guy as I wanted to avoid the itch 🙂

  39. Derek says:

    Hi Tim,

    I have been interested in a natural pool for some time but was really put off in the past by ‘professionals’ telling us that it is such a technical operation and cannot really be a DIY project. Reading your very informative blog, I am once again ‘pumped up’ to relook at this as an option. I have an existing fibreglass shell pool which I would be really keen to modify into a natural pool. The pool is approx. 4.5m x 9.0m and is about 1m deep in the shallow end and then going to around 2m deep in the deep end. I would also be keen to build an additional filter pool next to the existing pool in order to minimise the reduction of the swimming area. Is there a set depth that one needs to have in the filter pool or is it only the surface area that one needs to worry about? Thanks again.

  40. warren says:

    Hey awsome my wife and I are busy preparing our minds around the natural pool idea any reason why we cant just use a good plasterer and a waterproof paint (using the same construction method as you have done) what advice do you have 🙂 many thanks

  41. Tim says:

    Hi Warren

    No reason except even expensive epoxy coatings can be problematic. The big advantage of course is if there is a hairline crack in the plaster the fibreglass is strong enough to accommodate this – not may paints can. Also will they last as long?

  42. Tim says:

    Hi Derek
    Its all about the depth the plants will be comfortable in – my depth ranges from about 800 – 100 mm – but remember you can vary this height with rocks and pebbles or even planter boxes with the bottom surface a constant depth.
    Most of my plants like about 150 mm depth but the Water Lilies and bigger Irises like the deeper parts though.

  43. anton says:


    I want to order gravel. Is 13mm or 19mm the best?


  44. Tim says:

    Hi Anton – I used 19mm but only because that’s all I could get at Dec when I did mine – has worked fine. Main thing is you want to maximise surface area for bacteria to grow on whilst ensuring a flow of water (gaps).

  45. Hi Tim,
    Would love to feature your natural swimming pool in our online magazine. This month’s issue (April) actually looks at natural pools and it would be nice to be able to offer more information. Will link back to your post of course.

    Kind regards
    Janice Anderssen

  46. Christo says:

    Hi Tim
    I love your idea and also plan on doing the same setup. I have one question whats your water temperature I’m thinking of heating but dont know if I must or kan go that way. My pool wil only be getting sun up until 14:00. And if you can also try to assist in names of the plants it wil be mutch appreciate. Thanks for rhis site helped me a lot so far.

  47. Derek Marshall says:

    Wow, very inspiring! Thanks Tim.

    A few questions:

    1. What would happen if you connected the pump via an inverter directly(no batteries) to a solar panel, thereby only pumping while the sun shines? How crucial is continuous flow? Steping past grid electricty being cheaper that solar panels.

    2. My avalible space is quite shaded & all the terrace walls are south facing. Apart from the swiming temprature being cold, would the system still work in +-45% shade?

    3. Is heating totally out of the question?

  48. Anton says:


    You need to circulate the water 6 times a day. Every 4 hours or so. Not sure how the pool handle being stagnant for 10 hours a day.

    Shaded area is good for the pool. 45% is perfect.

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