About 7 years ago I started developing various water features, both garden ponds and water falls. As part of my research I found consistent comments like the following: you can’t make a natural pond using a pond liner without pumps and filters. The use of the word ‘natural’ here refers to the pond filtration system, not the esthetic look of the pond. I’ll deal with esthetics in a future post on how to build ponds.
In a natural pond the water, soil, plants, and animals all live in harmony. No one comes along to clean the pond or to aerate it. There is no big man-made filtration system that keeps the water clean. The common advice is that a pond liner is artificial and a pond built with it will never reach a natural state where the water, plants, and animals live in harmony the way they do in a natural pond. If you don’t filter such an unnatural pond it will become full of algae and the water will be dirty and smelly. The only way to have a pond with a liner is to add aeration and filtration.
Is this really true? Do you need pumps and filters to provide artificial pond filtration?
Building Natural Ponds
This blog post is the second most popular post ever on this site. Lots of people comment and are interested in more information about building natural ponds, so I have started a public Facebook Group to make it easier for people to discuss this hot topic. Please join the group at https://www.facebook.com/groups/1760349757565562/
What Happens in a Natural Pond?
In a natural pond animals (insects, fish, etc) eat, poop, sleep and die. Both the poop and dead animals add nutrients to the water. Some is added immediately, and some is added over time as the material is degraded by various micro-organisms.
Plants also add nutrients when they die. In fall all kinds of leaves and other dead plant material is blown into the pond, and as this material is decomposed by micro-organisms it also increases the nutrient level.
Algae is a plant that grows best with high light and high nutrient levels. When the nutrients get high enough, the algae takes over the pond and chokes everything else out.
Why does the algae not take over natural ponds? The answer is higher order pond plants (not including algae). Plants also use nutrients and as long as the plants in the pond use up the nutrients as fast as they are produced, algae has trouble getting a foot hold.
The secret to an algae fee pond is to control nutrient levels!
The other important part of a natural pond is the presence of micro-organisms. They are everywhere; in the soil, on rocks, and attached to plants. Think of these micro-organisms as the ‘cleaning machine’ of the pond. They take rotting, smelly animal and plant material and turn it into nutrients that plants and algae can use. The micro-organisms keep the water clean, and keep it from smelling.
A man-made pond made with a pond liner has no soil – so one source of micro-organisms is missing, especially if you keep cleaning the pond liner. Most ponds have few stones and few plants reducing the number of micro-organisms even further. Without microbes or filtration, the dead animals and plants just sit in the bottom, making the water cloudy and smelly. But it does not have to be this way – read on.
Controlling Nutrient Levels
There are a number of ways to control nutrient levels:
1) Don’t add too many fish. Too many fish results in too much fish poop. Koi poop more than gold fish.
2) Don’t feed fish. There are lots of natural things for the fish to eat. Adding extra food just adds more nutrients to the pond.
3) Have lots of living plants in the pond. With enough pond plants growing, they will remove the nutrients before the algae can grow.
Most man-made ponds are not designed to hold a lot of pond plants. Without the plants you need to add some type of mechanical filtration system.
The picture shows a pond at Aspen Grove Gardens during installation. The black pond liner is in the deep part and the planting shelves are covered in carpet (white/gray areas). The liner will be pulled up to cover the carpet.
Note the extensive size of the planting shelves compared to the total size of the pond.
Why Aerate a Water Feature?
A natural pond has no obvious aeration. There is no hidden pump creating air bubbles. So why is it needed in a man-made pond?
A poorly designed man-made pond does not have enough plants, and it does not have enough places for micro-organisms to live. As a result, dead stuff accumulates on the bottom. As this dead stuff starts to rot it uses up oxygen, and the water at the bottom becomes depleted in oxygen, which in turn causes anaerobic bacterial to grow. This type of bacterial loves the smelly mess and they thrive with low levels of oxygen. This seems like a good thing, and environmentally it is a good thing. The problem for us is that as they digest the rotting stuff, they make the water smell. We don’t like smelly ponds even if they are natural.
How do you get rid of the anaerobic bacteria? Simple, increase the level of oxygen by pumping air into the water.
Aeration is recommended for ponds so that they don’t smell and that works quite well. The problem is that without anaerobic bacteria, the sludge on the bottom degrades very slowly and so you also need to clean the bottom of the pond on a regular basis.
Think about this. Because you bought a pump and you aerate the water, you now need to do more work and clean the bottom.
Do Natural Ponds have Smelly Sludge at the Bottom?
Sure they do. It is quite normal to find this in a pond where a lot of animal or plant material falls into the water. You don’t normally smell it because the water is not stirred up enough to move the smells to the surface. Dig around with a shovel or step into it from a canoe and you’ll find the smell. The smelly sludge on the bottom is natural.
My man-made water features have sludge and anaerobic bacteria in the bottom. If I don’t disturb them, they degrade dead plant material, and produce nutrients for growing plants. In my ponds I don’t stir up the water so I don’t smell them.
Pond Filters
Virtually every reference on building water features recommends some type of filtration system for a man-made pond. Why is this necessary?
As mentioned above, the lack of soil in the bottom of the pond and the lack of rocks and plants results in an environment that houses few micro-organisms when compared to a natural pond. The solution is to provide a man-made place for the microbes to live. Most filtration systems contain some type of surface for the micro-organisms to live on. This can be sand, wool, small pieces of plastic – it doesn’t really mater. What is important is that there is a lot of surface area. Microbes like to attach themselves to a surface and then ‘eat’ plant and animal bits as they float by in the water. So the filter replaces the natural places were microbes live–on soil, rocks and plants.
In nature the microbes live in the slime you find on rocks. It is healthy for a pond.
Water Feature Myth
The above information should give you some background to understand both natural and man-made ponds. If you think about it for a while you will realize that a properly designed pond, with enough pond plants and homes for microbes, should work just as well as a natural pond. When I was planning to build my ponds I spent a lot of time trying to find a reference for a man-made pond that worked without pumps and filters – I found none. Every reference I found said that such a pond will not work.
I set out to prove the experts wrong.
The following is not the result of good research or the opinions of experts. It is the result of my experience with two ponds over a 6 year period. In this blog I am not describing how to make a pond but I will do that in another blog entry–some day. I will provide the key points to consider.
Based on the information above, a pond design needs two things which are lacking in most designs. It needs lots of pond plants. Plants will use up the excess nutrients and keep the algae in control. It also needs lots of little homes for microorganism – they will help keep the water clean.
The following are some key design decisions:
1) Wide planting shelves. My pond is 20 x 30 feet and about half of that area is in the form of planting shelves that are about 8 inches deep.
2) Soil is not used for the plants. Pond plants don’t need a substrate, except to hold them down, and the pond certainly does not need more nutrients from soil. The plants should be using the nutrients produced by the micro-organisms and not the nutrients in soil . Instead of soil, I use small rocks – 1/2 inch or so. I just use all the small rocks I collect as I make new flower beds. Don’t fertilize your plants.
3) Pond plants are not in pots. I just place them on the small rocks in the planting shelf. A larger rock on top holds them in place until they root.
4) The sides of the pond are lined with rocks adding more surface area for microbes.
5) A deep planting shelf (about 2 ft deep) is also present for waterlilies. It is important to cover 2/3 of the surface water to reduce light getting to algae.
6) Goldfish were added to feed the plants, and eat mosquito larvae . They are never fed. They grow quickly and breed regularly.
The garden pond in the pictures was built 5 years ago and it is only now that the planting shelves are starting to be full of plants. Wild bull rushes seeded themselves the second year. Irises have been added and are spreading. The pond has never been drained, and the bottom is never cleaned. It has no pump and no filter. Wind is the only thing that might provide some aeration as it ripples across the surface of the water. There are several large trees around the pond that add fall leaf drop – which is left to settle in the pond.
For the first 4 years the pond plants increased in number each year. During this time, I did have string algae, but it mostly had a spring bloom and by mid summer it was under control. The water was very green showing the presence of lots of one celled algae, but the water was clean, and it did not smell. The fish that were added the first year did not over winter but since year two they have overwintered and keep breeding. Herons and racoons help to keep numbers in check.
From a naturists point of view the pond is very healthy with lots of frogs and dragon flies breeding each year. Larger mammals, including deer use it as a water source.
It is now nearing the end of summer 2013 and the pond has been extremely clean–much clearer than the picture below from 2012. In fact it is too clean. You can now see the pond liner in the deeper sections of the pond. There was no string algae this year and almost no one celled algae. It has been a strange year weather wise which may account for some of this, but I think it is mostly due to the fact that the planting shelves are now very full of hungry plants which are out-competing the algae.
After 5 years I conclude that aeration and filtration are ‘probably’ not required. I’ll need to wait another 5 years or so to be absolutely certain of this. It is possible that in a few more years the stuff at the bottom will overwhelm the pond and may need to be removed. I doubt it!
String algae is gone, but one celled algae is still making the water green in late summer. Note the number of plants in the water.
As plants grow and get larger, algae is almost non-existant.
Is Green Water Bad?
From an environmental point of view there is nothing wrong with water that contains algae. In a natural pond it might indicate that too much fertilizer has leached into the pond which is not good. But this is not usually a problem in a man-made garden pond. If your pond water is green with algae it is probably healthy.
You might not like the look – that is a different matter.
In Japan, garden ponds are treasured and it is common to buy a dye to color the pond water. Why do they do that? When the water is colored it reflects light much better. The shadows and reflections are considered to be very desirable. So next time someone comments about your green water, just tell them that you do it on purpose to better enjoy the reflections.
If You Have Questions
If you have further questions about building natural ponds or about your existing pond please post them in our new face book group called Building Natural Ponds.
Beneficial Pond Bacteria
natural ponds do not need to have bacteria added. For more on this topic have a look at Beneficial Pond Bacteria – A Waste of Money.
Related Posts
Winterizing Ponds and Water Features
This is a brilliant post! Thank you
I just want to say how happy I am that someone else agrees with me about this subject! I have been saying for years that ponds are cheap to put in and cheap& easy to maintain without electricity! I use rinsed lava rock as a home for my bacteria, they love the nooks and crannies. And lots and lots of bare rooted plants. That’s all it takes!
However I must admit that I love spitters, so I always add a couple and make sure their output is flowing over pea gravel, lava rock, or plant roots. One or two of these totally clears up the green, but then yeah, you can see the bottom liner.
One trick I enjoy for covering the water surface is to use Impatiens. I rinse off the dirt (of course) then poke the roots through a foam meat tray. It will float and the flowers will quickly spread to hide the tray. You could anchor the trays, or let the breeze move them around.
Again, so glad to see this post. Keep spreading the word!
Brilliant! Thank you for the idea of the meat tray! I have been puzzling about how to float my pitcher plant without it looking doofy.
what are “spittters” mentioned in a comment?
Spitters are statues that have water routed through them, so it looks as if they are spitting the water out. They come in all sizes, frogs, turtles, angels, herons, all kinds of things. They will have a place to attach a hose from your pump on its back or bottom side. The water then flows out the figure’s (usually) mouth.
It’s not that forceful, but any water flowing over any bare roots is beneficial to the pond. And it gives that wonderful sound of moving water!
Thanks for this unique bit very useful idea using the meat foam trays. I live in southern USA, zone 8. My tiny koi/goldfish pond needs plants lots of plants but I have no plant shelves. I’m hoping this idea will work in interjectingreat plants into my pond which normally would need shelves.
Wow! Great idea with the foam meat tray. Have you tried this with any “pond” plants? My pond is in shade under lots of trees.
Hello
I left a question 6/28/16 and there has been no response. Just checking to see that I sent and responded correctly because it still says “Your comment is awaiting moderation. ”
Thanks. Hope to start on the pond soon.
Gerry
If it was not answered it got lost – post again.
Two years ago when I was deciding whether or not to bring back to life an empty concrete pond in the backyard of the house where I now live in Las Vegas, I came across your site. Although all the stores Out Here Sell filters and big pumps, I decided to do my best just to let my pond create itself naturally following your guidelines. Now in its third year, the pond is doing great. I have a couple small pumps in there just to splash water around for my amusement. The Goldfish seem to like 2 sit in the flow of water. But other than that, the pond has just been going on its own. All my plants came back from last year. My cat tails are spreading. It’s really a gorgeous and relaxing addition to my yard. By the way, it’s about 20 feet across and only about 8 to 10 inches deep.
Glad to hear my methods work. In Las Vegas you don’t need to worry about ice on the pond – lucky you.
Fascinating write-up! I’ve been considering digging a few mini-ponds in my yard for years. Two questions:
1. I’m in southern California; our average summer highs are in the mid-80s Fahrenheit, but mid- to high-nineties are not rare (heat wave two weeks ago reached 107!). I’m not sure what your max temperatures are in Ontario, but how do you suppose higher temperatures would affect the results you’ve seen?
2. I don’t have a lot of space in my yard, so my ponds would be fairly small. Have you experimented with smaller ponds; and if so, what do you suppose a minimum size is to support a functioning ecosystem (that can keep the water clean without filters, etc.) would be?
Higher temps won’t change things except more evaporation.
I have not worked with very small ponds, but they would be more difficult to keep in balance.
I have had several small ponds and have found that it needed a little help. If you add water flowing over your bare rooted plants, you’ve just made a fabulous filter! I’m always on the lookout for cheap small pumps, often I find table top fountains that are crackled and discounted. But the little pump still works and works well in the pond.
Some great plants for this are mini cattails,water hyacinth, and various rushes. They are heavy feeders and will help keep pa pond clear.
The temp will increase your algae load as well, keeping a lot of the surface covered with plants/lily leaves/etc. really helps. Water hyacinth really loves the heat.
So happy to find your post Robert! We followed your suggestions. Put in our 8 x 15, 3 foot deep lined pond with plant shelf, lined with stones and marginal plants. The marginal plants are anchored in the stones without soil. They’re alive but not growing much. Two water lilies in soil are growing very well. Water hyacinths slowly coming along, but duckweed very slow to grow. Pond is 8 weeks old. Is there simply not enough nutrients yet for the plants? The water was cloudy in the beginning, but crystal clear for 5 weeks. We added five small goldfish 5 days ago. They look very happy and eating from the liner. Will the fish be adding nutrients for the plants now? Do we risk starving the plants and/or the fish? Hope we’re doing this right – we’re having a blast!
Fish poop will feed the plants. No worry about starving fish or plants. Just give it time.
As Robert says, it takes time. Plants will take a season or maybe even 2 before they get larger, just as in planting perrennials in your land garden.
Are they getting a good amount of sunlight? If it’s shady, they’ll take longer to grow, but they will grow.
Also be sure they are planted at the appropriate depth. Many marginals only like a little water on their feet, others prefer to be submerged. If the shelves are too low for some of your plants, try potting those plants in a pot (like the cheap plastic ones they come in) but don’t use soil! Use some pea gravel to pot it. Then prop that potted plant up on a brick or rock to the appropriate height.
That said, adding bricks to the pond, or concrete blocks, will alter the water’s pH. If that’s a worry to you, avoid them. I used both many times and my solution to the pH issue was simple. I threw away my pH tester!! I stopped testing my water and never did a thing to correct it, and just let nature take its course. And never had any issues that I could tell. My fish and my plants grew and grew and grew!
I read your article on DIY natural ponds in the Oct/Nov 2015 Mother Earth News. I am thrilled to switch my tiny store-bought pond, which can not stay clean even with a pump, into one that will be self-sustaining.
One question after looking at rocks at the stone store: which rocks are best for plant shelf areas – smooth, like river stones or porous, like lava rock?
Thanks.
The goal is to have as much surface area as possible for bacteria to grow on. Lava would be better than smooth for this. Small is better than large. Cheep is better than expensive.
Careful with lava rock, it’s extremely abrasive to your liner so if you do use it don’t put it under any pressure like walking on it, you are better off with small pebbles for planting.
First, thank you for sharing your experience! I’m so relieved to read about your success with pond without filter because I’m hoping to do the same. I have a 100 gallon stock tank with 2 small goldfish, 2 small koi and 5 minnows. The plants were growing slowly until I added the koi fish. I thought of cleaning the bottom of the pond but the bottom is covered with mulm (I just learned this word!) and roots from the lily plant I’ve had for 10 years. To clean it means pulling out a whole sheet of roots. Should I leave it alone? I don’t want to touch it. All the fish are happily swimming around, even rooting the bottom. Water is a little bit green but I just added some more plants and hope it will clear up in time. I don’t know if the pond will accommodate the growing fish without filter but I’m hoping it will. To be honest, I’m scared because every store I went to told me otherwise. By the way, the pond went through 2 years with just a handful of minnows and I’ve only added the other fish 2 months ago. I’d appreciate any advice. Thank you!
You probably have too much fish for 100 gal – maybe not today, but fish grow. For large koi it is recommended to have 100 gal per fish.
I would not clean out the bottom. Microbes live there. If you start getting a lot of stuff at the bottom, it does not hurt to fish some out from time to time, but don’t clean the bottom.
I don’t blame you for being concerned. Why believe me when all of the stores and other web sites tell you you need pumps and chemicals. I was in the same boat 8 years ago, but I did not have even one person say it would work.
I will be publishing a book in spring about creating natural ponds following the ideas I have presented in this post.
And why do you think all the stor es and magazines tell you to use pumps, filters, UV lights and chemicals? The pond business is a booming one, and if they tell you to go natural, they won’t make money. Their object is to sell.
That is certainly true. A lot of this is also in response to koi people. They like lots of large fish in a pond, and when you do that it is much harder to go natural.
This is really no different than other forms of gardening – most of the stuff being sold is not needed.
Air pumps are sometimes used to move a little water in small ponds.There are several articles online that you can read .Research the subject.I once had an indoor natural aquarium and used weeping willow branches to get rid of the green algae.The fish took care of the plants and the plants cleaned the water.Perhaps you can plant a small willow at the very edge of your pond .Willows will grow in standing water.(Get a small species)
Air pumps are used in large ponds and they seem to reduce algae. Or make the pond with plants and you don’t need the air pump!
I doubt willow will reduce algae – but if you have a scientific reference to show this works I’d love to review it.
Hello. I’ve had a 100’x30′ pond, up to 10′ deep which I had made while leveling out a place to build my barn. It’s fed by run-off from the hill out back. I was wanting to aerate the pond because I thought it would make it clearer and look nicer. After reading your article and many of the comments, it seems I’ve been real lucky.
I’m in southern Ohio. My pond was dug out, earth pushed into place for a dam and a low area for over flow. That’s it. I have a lot of frogs! Some fish were thrown in from time to time, but no one has caught any for years. I do have three large turtles, about 12 to 15 inches in diameter that have hit a fisherman’s line. Right now I have quite a bit of algae. It doesn’t smell at all. There’s plant life in and around it.
I want to add a waterfall from up the hill which would be about 60′ away and I’m thinking 20′ up. Line it with washed gravel about 3/4″ to 4″ in size. I’m thinking that will clear up the water somewhat. What do you think?
Later this year or next, I’m planning a greenhouse and did some research and would like to try to have the pond fertilize the plants while also adding a editable fish. Any advice? Anyone?
The waterfall will aerate the water which is good for animals and plants. The rocks in the waterfall and river leading to the pond will get covered with bacteria and they will help remove nutrients from the water – that is good. I doubt it will be enough to remove the algae from such a big pond, but it will help.
Pond water would be excellent for watering plants. By removing the water containing nutrients resulting from decay, and replacing it with fresh water you should also reduce the algae.
Hey i read the comments down to june 13. Is the book out yet and whats the full title? Did you ever get to those articles on winterizing? You asked another poster to refrence research data, do you have a collection of such things, would you mind sending it my way or making it accessible? I have no interest in the cancer that is facebook, is there any other way to access the information there as i will not use the web page. The main problem it seems you suggested from this artical is build up from debree in the bottom of the pond, i am assuming the hypothesis is over time the pond will fill in, was a solution ever found?
Good luck to all of you. Have wonderful lives.
The book is out and called “Building Natural Ponds“.
We also have a Facebook Group called Building Natural Ponds where we discuss many of the questions you are asking.
There is some discussion on winterizing ponds in my book, but I have not published any articles on the subject.
no mention is made whether new water is flowing in and out of your pond… it seems if you do not recycle new water, the whole pond will get rancid and fish die and everything get bad.. or am i missing something ?? thanks!
Hi Shantum,
Our pond has no groundwater source and it’s doing very well, supporting frogs, fish, turtle, snails, toads, microfauna, etc. Most of the time, ordinary rain is sufficient to refresh the volume. Occasionally, we add a few gallons of well water through our hose. As Robert emphasizes, plants are the critical element of man-made pond health.
Shantam, in a well balanced pond, with lots of bare rooted plants, and rocks/stones for algae to grow on, there is no need to recycle the water. The pond will clean up its water by itself. Microbes will flourish and consume the fish and plant waste, producing nutrients for the plants to consume and grow, and on and on. I don’t know the science of it, but I do know that it works!
If you scoop up the muck from the pond bottom, it will stink like nobody’s business! However that is exactly how it’s supposed to smell. And so long as you leave it alone on the bottom, you’ll never even get a whiff of it.
Plants, plants, plants!! (and no soil!)
We are nearing the completion of our pond and have always planned to go natural with no artificial filtration. Yours and Robert’s comment about stirring up bottom much makes me wonder, though, will a waterfall with pump to run it stir things up such as to create problems with smells and high turbidity? This question undoubtedly shows my experience, not having yet engaged my pump! Thanks, all!
Material will settle away from the waterfall and pump, therefore running the pump does not cause a problem.
Hallo from Brussels.
I have a pond (5m/5m/1,5m) with KOI in my garden (in the middle of the city) with filter and pump. It came with the house when I bought it. I never had any experience with ponds or fish. They are doing well (10 years)
However, I love your approach and want to try it. First adding lots of plants and then gradually diminishing the pumping and filtring.
The bottom slopes from a depth of 5 cm to 1,5m. There is ample room, rocks and pebbles to have many more plants than I do.
Two questions:
1. can’t you really tell something more about the kinds of plants that are most efficient for nitrates etc…. I understand it depends on the climate, but not even something about the genera?
2: my KOI eat the waterlilies. alternative to provide shade in summer?
With kind regards
I really don’t know which plants use more nitrogen, but probably the ones that grow the most leaf material will use the most nitrogen. Use plants that other local ponders use. I use iris, cattails, waterlilies and marsh marigolds a lot – but they grow easy here. I am also in zone 5 and want things that survive the winter. I am sure Brussels is a bit warmer so you have more choices.
Koi and plants don’t get along very well – the fish eat and disturb the plants. You might have to keep the plants and fish separated. I don’t have an alternative solution to waterlilies since koi will eat most floating plants.
How about using some type of plastic fencing in the water to separate the lilies from the fish? The plastic won’t rust, a neutral-colored plastic will be hard to see, and if the mesh is small enough, it might keep the fish from getting to the lilies. I don’t know if this will work (especially in a 5mx5m pond), but it might be worth a try. The mesh could be weighted at the bottom, suspended (from a float?) at the top, and possibly anchored to the sides of the pond (to create a “fish-free zone). Just a thought….
I have not tried that but it sounds like a logical solution that should work.
Mini-cattails, water hyacynth, water iris and various rushes are great for cleaning up a pond! I love blue rush and corkscrew rush myself.
One possible method of keeping your koi away from the lilies, is to make a floating net island. Get a hula hoop, hang a length of black tulle around it, making sure it’s long enough to reach the bottom of your lily pot. Place the pot inside the hoop/net contraption and let the hoop float above. Just be sure to check daily, to be sure no fish jumped the hoop, and needs to be rescued!
Also, a good idea for providing shade is to make impatiens islands. The impatiens flower loves the water. Take a few plants, rinse off the dirt from the roots, then poke the roots through a clean foam meat tray. Float this in the water. The flowers quickly fan out to cover the tray. It provides shade as well as more roots to clean up your water! Plus they are very pretty floating around!