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
Thank you for sharing your findings! It has inspired me more now. I’ve lwys wanted a pond but have always seen them as too much of a hassle with filtering and pumps and other jargon that I don’t have time for. It seems you have made a self sustainable pond that requires no maintenance. I am planning on making one that is only about 4ft wide. Would a big plastic based container change anything rather than using the lining? Obviously I would still need to add rocks to make shelves to increase the surface area. Is digging a hole and using lining the only way to go? Thank you
There is no real difference between a hard plastic container and a liner. The problem with hard plastic is that you are limited in size. If you take a 4 ft pond, and add rocks for a shelf, you will end up with a 2 ft pond – which is getting quite small. Liners allow you to make ponds bigger. You could use a 4 foot pond, and have the shelves in addition to this, making the liner size 6 ft.
Hi. Im super excited to have read this article, it was filled with tons of information that I needed. I too am looking for a way to start a pond without filters and pumps. This is my story… I have a 10,000 gallon pool just sitting in the back yard, full of everything under the sun. I have leaves, sticks, snails, minnows, and who knows what else. Theres quite a bit of algae in there as well. I bought a pump that would move 250 gph of water and microabial algae clean. I dont mind leaving the pump in there, as I am running the water into the preexisting water fall. I felt this would help get the water moving a bit. I wanted to add gravel and plants into the water fall, this I would hope to help filter the water as it comes up through the gravel and plants. What other advice would you have for me to get this pond up and running successfully. How many plants, what types, and what grows at 7 ft deep where all decaying leaves and such are?
Thank you kindly.
Pumping water through a gravel bed should be a very good filtering system. I almost added one to my water fall, but decided against it for the reason that if it ever got plugged, and they do, it would be a big job to clean out. For me there is also the issue of things freezing and cracking in winter.
I don’t know of any plant that grows at 7 feet deep. You could build up islands to a more shallow depth and plant on those. You can also add a floating island which I just researching now. the floating island would allow you to have more plants using the nutrients in the water, and cover more surface area keeping sun from the algae.
Hi…im so happy i found ur blog…i am really looking for miracles to create a pond without pumps or filters or other machines or tubes ‘coz it will cost a lot…heheheheh… i am about to make a pond this summer vacation… in ur post, you said “pond plants are not in pots” and u have those planting shelves… is it ok if i’ll just put the plants which are actually in pots into the pond? Or is it really necessary to remove the pots and just put the plants into stones wthout any soil? thanks! 🙂
There is nothing wrong with using pots. What you will find is the plants will start to grow outside the pots over time. When they do it becomes difficult to get them out of the pots in the future, but the plants don’t care if they are in pots or not.
Brilliant article. I have been seeking clear concise information for years. My man made pond is approx 16 ft by 3 ft with depth about 12 to 18 inches,I have a pond with a lining, 12years old now.
I was encouraged to get a pump with centre fountain.I have about 8 goldfish born in the pond. Some have died or plucked by a Heron! The pond is in full sun pretty well all day.
Last year my pond became full of what looked like soapy bubbles. I didn’t know what to do. Finally I applied a powder to breakdown the leaves and rubbish at the bottom of the pond.
Only when it got colder did the foam finally disappear.
I am not sure that was the right thing to do and still very unsure what to do this year. …?
Not sure why you have bubbles. The decaying material in the pond will produce gases, but these usually just escape into the air–especially if you have a fountain going. Sorry I can’t help.
I started getting bubbles in my water when my algae started to die. If you put any kind of algecide in the water this is what happens anyways.
I do believe your goldfish were spawning, that’s the foamy stuff you saw on the pond. The first time I saw it I too wondered what it was and was horrified to think soap had somehow gotten in my pond. I tried netting it out, The second year it happened I just left it because no harm had come to the fish the year before, then to my amazement about a month later we counted almost 50 baby fish, hiding among the rocks and plants! Hope this helps
I am in the process of digging a natural pond and found this post extremely helpful. The water table is so high here and the soil is so clay heavy that I feel this may make it possible to do without a liner. It is half full the day after digging it out without any supplemental watering… I have some questions regarding a 1000 gallon pond, 3 1/2 feet deep at maximum :
1) If my water level fluctuates by about 10-12 inches during our dry season, are there any plants I should specifically avoid that don’t do well with this fluctuation?
2) What are you thoughts on no fish at all, and just keeping a turtle/frog population in place?
3) I was going to put some sand in the bottom as well as occasional large and small rocks. What are your thoughts on decaying wood floating around or dipping in from a shore line?
Thanks for your time and expertise!
Water plants are used to water fluctuations. What is important is that at the low levels, the plants are not sitting on dry soil. As long as the roots stay wet they can take the drying. My pond will go down by 8-10 inches if we don’t get rain.
You don’t need fish. In fact I am quite sure that my fish eat most of the tadpoles in my pond. If I did not have fish i might have a lot more frogs. One thing to watch out for are mosquitoes. Fish do eat mosquito larvae and keep them out of the pond. Other wild insects will also do this, so long as your pond does not breed mosquitoes you don’t need the fish.
If you ever decide to clean out the bottom, the sand and rocks in the bottom may be a problem. It is hard to clean with them there. Large rocks are no problem an I think they are important for making the pond look natural. Real ponds have rocks sticking up in the water – most man made ones don’t. when I made my pond I made sure to add some large ones right in the water. Logs would also be a great addition, and wildlife will love them. Turtles, if you get them, love to sun on them.
I have 3 care lot and I am researching to build a pond. I love to have nature pond without even liner, but some people said it will hold very low water during winter (Florida), I am not sure if I dig deep pond and opt opt out the liner is good option? I have to go 15-20 ft deep. I want to do 30×50 ft pond.
my second question if I use the pond water for irrigation, would this be very good for my garden and clean the fish waste? I will have mechanism to refill the pond (if I go liner but omit if I go 20 ft deeper)
thanks
Making ponds without a liner is a different story. Success depends very much on your local conditions. I suspect in Florida you can dig down and find natural water in many places because much of Florida is reclaimed land which is very close to sea level. In other places a hole will not hold water unless the soil forms a clay barrier. You really should get some expert local advice on the liner.
Pond water, including fish waste is very good for the garden. You will be watering and fertilizing at the same time. This is provided that the pond is full of fresh water. In Florida you might get salty water coming up from underground if no liner is used — that would not be good for plants.
Hi Robert, thanks for such informative article. Hope it would encourage more people to build pond the natural way.
I converted my swimming pool into a natural pond, it’s on its fourth years now and have never used a single watt of electricity . Never changed the water either, and all is going well similar to what your pond.
That is good to hear. I am not the only one with a natural un-natural pond.
Dear Sir, Thank you so much for your article on ponds without pumps. I will be taking your advice this spring when I (rebuild) my starter pond from last year. I just want plants – no fish, maybe a frog or two, a place for birds to take a bath. Now I know its okay to have less than clear water and plants without pots and dirt. Wish me luck.
In my experience frogs come very quickly once water is in place. Good luck.
Hello from the Western Cape – South Africa. Thank you for the insight and authentic wisdom – I have learned a lot. Hmmm am busy developing a water pot that can host my waterlilies because my Bull-terrier thinks it’s food LOL – I am not so sure of not having the plant in a pot with soil but will follow your advice – God bless!!
I love your pond!!
So good to read your post Robert! I created a large pond about 6 or so years ago and have been using pumps but the work they entail is too much! I’ve got a fair amount of plants and plenty fish and frogs too now. The look is green and friends all tell me I need to drain it and clean it but I’m with you – you don’t see nature emptying and cleaning natural ponds! Thanks again, great post!
This is the best site for support for no filter ponds. My little 50 gallon pond is still going strong it a morph of some smaller ones I had for some years. Still have my ghost shrimp from way back too! It is full of hornwort, dwarf papyrus,dwarf cattail a few dwarf liliys. Has some platys to eat the mosquitos. My only cheat is a very small 12$ solar pump to occasionally circulate the water. Only works when the sun is out and I dont fuss over it at all. The best thing was this summer when I was thining out the hornwort I found fresh water sponges growing!!! How cool is that! This little pond never fails to surprise.
That is cool. Here is a video of some fresh water sponges https://www.youtube.com/watch?v=ye6yMd8ldm4
Wow! that was a cool video. My sponges are not as large, more like the smaller ones coating some of the branches. Fresh water life is not as appreciated compared to saltwater, it seems.