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
Hi Robert! Love the article. I have a small 10 by 10 pond that I raise waterfowl on. (3 feet deep in the middle) I have a drain in the middle and I’ve been just pulling the plug every week or so to clean the water. I’ve often wondered if I let it go natural if it would work with waterfowl and all their poop. What do you think? Thanks
I don’t know anything about waterfowl, but I am guessing they would add a lot of fertilizer to a 10 x 10 pond, which would result in a lot of algea.
BTW I am from the UK
I love your pond and your very helpful post 🙂 and wonder if you would advice me:
I have a teeny 11gallon preformed pond (few weeks old) which I hope to attract wildlife, frogs etc to get rid of slugs and snails. I have bought a basket of marginal plants which sit nicely on the larger shelf but the slugs /snails (I think) have immediately started to devour the leaves totally leaving only the stem on one of them, as they were expensive it has put me off buying more do you suggest anything?
I also see what looks like long trails of green excrement on the white rocks I have under the surface and wonder what is making it? TIA
Try to buy plants that are plentiful in your local ponds – not exotic plants. If they survive locally there is a better chance the local population of slugs will leave them alone.
I suspect that the green excrement is from frogs or toads. This video might help https://youtu.be/lmoPMiCJ10A
Hi Robert
Thank you for taking the time to reply and so quickly 🙂 great advice about the slugs thanks, the plants are local plants bought from my local garden centre.
I am surprised and excited to think that frogs or toads may already have found my tiny pond (2-3 weeks) so thanks for the (cough) interesting video, they sure make a mess but the trails I am seeing are much narrower??
After seeing the video I am now wondering how difficult will it be for me to keep the correct water balance; I don’t want crystal clear water as I want it to look natural, but also would prefer not to if possible, see lots of trails covering the stones which are right at the front of the pond (viewing point), placed to act as a sloping area do I need to remove the excrement to avoid it overtaking the pond or is it good for the pond? TIA
What ever kind of excrement it is, it does contain nutrients. Too many nutrients in the water and algae will start to grow. How much is too much – hard to say. It depends on the amount of water and the amount of plants.
Thank you so much for your informative post. For about a year now, I’ve been planning a two-section pond with a connecting “brook” and a waterfall. I’ve done a lot of research and love the information you give about doing it naturally – without the use of electronic equipment. My question is can I still have the waterfall without a pump? If not, what will I need to have?
Maybe I don’t understand the question, but water does not run up hill on it’s own. A pump is needed to move the water to a higher level so it will flow down, causing the waterfall. There are many types and sizes of pumps and picking the right size is not easy – boy – that is a helpful statement 🙂
If you are just starting out with waterfalls, and the system is fairly small (preformed ponds usually are) then I would get a submersible pump. They take a bit more work to keep them clean, but they are easier to install, and they usually cost less than an external pump.
The key to pump size is to use the largest hose possible from the pump to the top. A large hose means less friction, and more water being moved. In turn this means you can use a smaller pump. I suggest you to talk a store selling ponds and ask them to size the pump for you. You will need to give them the size and height of your system. They will probably try to sell you a small hose – insist on a larger one. Many pond ‘experts’ don’t understand the importance of this.
My main water fall pumps water to a height of over 10 feet and a distance of 40 feet. I see very little loss in flow because the hose going up the hill is a 4 inch diameter pipe that is very straight – very little friction = maximum flow.
hi Robert, in researching for my turtle pond you’ve helped a lot, here’s some cool links for liner less ponds, http://www.permies.com/t/3409/ponds/Gley-technique-sealing-ponds-dams and http://www.nwedible.com/can-you-seal-a-pond-with-clay-kitty-litter-2-html/
the only thing i worry about with this, is if you’re in an area that freezes your fish and turtles will need to hibernate. they go to the pond sludge to stay warmer, and say hidden from predators. anaerobic bacteria produces more “dangerous” chemicals than aerobic, so your fish might have more problems. granted, most koi ponds and such are seriously overstocked compared to natural/wild ponds, so that’s gotta be part of the problem. if you have a source for it, adding pool filter sand(high grade quartz sand, nontoxic) provides a beautiful, cheap, consistent substrate for plants and particularly bacteria to grow in, but i’m betting that’d only work with a lined pond, otherwise the sand would probably add too much drainage to the soil underneath. if you wanna know whether you need a liner for your pond, dig a hole next to where you want your pond, and dig it as deep as your pond will go. fill it with water. see how long it takes to drain. if it’s less than a week, you’ll need some serious amendments to your soil, or a liner. less than a month, some ammendments, but not much. a month or more, you can probably get away with not amending your soil, but i’d say add bentonite clay, or use the gley method linked to above to get some good stuff. duck poop will help seal in linerless ponds over time. and duck poop a lot.
Fish, turtles, and fogs do hibernate in the bottom, where the CO2 levels are highest. If a lined pond freezes over, for a long period they will die.
A linerless pond will always loose some water. It becomes a function of how fast it looses water, and how much you will tolerate. Bentonite does work.
Hi Robert. This is great advice – exactly the kind of thing I am looking for. I care for a flock of chickens and outside their coop is a large concrete depression that I really hope to make into a (low-maintenance) pond. I would love your plant recommendations, besides irises. Also, any advice on how to make the planting shelf when the sides are sloped? Should I still use a plastic liner and the carpet material for the shelf? Thanks so much!
As far as plants go, use local plants where you live. They obviously like your climate.
Once you have sloped sides, it is not really feasible to make planting shelves. You can however, uses pots right in the water, either sitting on the bottom or raised up with some rot-proof material.
Devery Wallace
I have a pond that is built on my deck it is a box and with plastic lining structure using a pump that sends water up to a fountain . There is no ledge to put plants and rocks. We have some plants, adopted snails and lots of algae. Can you make suggestions to help minimize the algae that is in the pond as well as hanging from the fountain.
Small ponds are more difficult to keep free of algea. Add more plants.
Dear Robert – thanks for much for this article. We rent a lovely little home with a fairly large (large for this small backyard) pond (approx 8-9 feet in diameter – although not a circle – and 5-6 feet deep) with a creek-like waterfall feature. Because the pond does NOT lose water when the filter is off and the creek isn’t running, we suspect there is a leak in the underground piping (loses lots of water when the creek is running). The liner has been repaired and I’ve been looking for a way to keep the pond lovely without the creek running. Your article and the responses to it have helped me understand a different way to keep the pond beautiful. So next year we’ll try a “dry creek bed” and a pond with some floating islands.
Addendum to above comment: we have no fish…..
Hi
Could you advise me please? Can I apply the same guidelines for a natural pond to very small ponds? Thanks
Probably.The problem with small ponds is that there is less room for error. But most of the principals I discuss apply.
Hi Robert,
Our one-month old 19 x 12 foot pond is undergoing an algae bloom, I think, in the form of a soft brown mat on all surfaces that is now also clouding the water. Tiny fragments (perhaps dead?) are floating on the surface. It’s been hot here, so it’s not surprising. What affect might this have on the five small bluegill sunfish in the pond? We also have frogs and snails. We are slowly adding plants, but we need many more- it will take some time. We don’t mind algae but would like the water to support other life forms as well! Thanks for your expertise.
Pond life will be fine. If a lot of algae is dying, it will reduce oxygen levels in the water which is not good for fish. If you see them with their mouths at the surface of the water – they need more oxygen. then you might remove some of the dead algae.
Until you get more plants you can always remove some algae. But it is probably not necessary.
Glad to hear it -thank you!
Just my bit for the topic: I have a pond with pump installed. I bought a pump and filter including UV lamp for sole purpose to solve green water algae. It did work, but UV bulbs need rather frequent replacements, so its not too practical solution. This year, we made a small reconstruction of the pond, made a small brook with waterfall, using the output of the pump. Since reconstruction, i didn’t see green water algae even after many hot days. The water is crystal clean now, like in some alpine lake. Before, when we didn’t use a pump or used the pump output go directly to the lake, without UV lamp it did not prevent green water. This small stream + tiny waterfall is trully a win-win – it does look and sound great and does the perfect job in water cleaning…
I am surprised the brook and waterfall made that much difference, but all of the rocks in the brook are now covered with bacteria, and they are helping to keep the water clean.
Hi Robert,
We have built a pond about 19 feet by 12 feet, with depth from 1 to 3 feet and lined it with the 45 mil EPDM, in Pennsylvania (zone 6). As we start adding plants, do we have to be concerned about the roots eventually damaging the liner? Thanks for your great posts.
some sources say this can happen – but I doubt it. I tried to use a utility knife to puncture the liner – just to see how easy it was to get a hole. It was damn hard. I doubt roots can puncture it.
Oh!! I love this! Six months ago I stopped putting chlorine in my 20′ by 40′ swimming pool and turned off the pump. I had done lots of internet research but only found one place that said it was possible to go pumpless.
That gave me courage and knowing that it was reversible if it was a horrible disaster clinched the deal. It was pretty ugly at first but I was determined, and impatient. The second month I threw in a few big scoop shovel fulls of rabbit manure to help “feed the bacteria” I wanted. Bad idea but not fatal. Now my ammonia levels are still too high for fish to live in but my plants are fantastic.
I didn’t want to fill the pond with dirt or stacks of tires or bricks as some had done but needed a way for the plants to be in shallow water. Then on you tube I discovered floating islands for ponds.
https://www.youtube.com/watch?v=P28PNf2JjF0
I adapted them and went out hunting for wild plants, begged plants, and even bought a few. Now I have lovely floating islands that sail around in the breeze like swans gliding. Some plants like the duckweed and water primrose just go crazy, trying to take over, but I like them as compost around my fruit trees. I just rip it out and throw it at the trees’ base. My ammonia levels are slowly coming down and soon I’ll be adding some catfish, bluegill, and perch. Even now the frogs, dragonflies, and other small creatures are moving in.
I wish I had found your blog when I first started. It’s wonderful. Thank you so much.
Sandra – thanks for the link to the plant islands – I watched several videos and am looking forward to trying this. My pond needs so much water – the liner has been repaired and there was no problem when the filter is off and the waterfall feature isn’t running so I suspect there is leaking in the inground piping. So next summer, I don’t want to use the waterfall feature – just the pond without a filter. This is so helpful.
I’m so glad the island links were helpful. I’ve learned a few thing building my own islands.
+Don’t put dirt in them. I’m still trying to figure out how to clear my water of the suspended dirt.
+If you buy plants in pots they’ll be fine if you just take them out and dump them in your island.
+The plants GROW! Duh. Allow enough room around plants that will get bigger so they don’t flip over. (Don’t ask. lol)
+Mint LOVES growing on islands.
+Don’t try fancy shapes. Circles are much more stable.
+A dollar store laundry basket with Pool noodles zip tied around it is an easy island.
+Use black zip ties. Lots of them.
+If you have free floating islands they will decapitate your lilies.
+If you’re planting standard cattails make a deep (couple of feet) basket so more of them is under water to balance the height.
+So far I know Papyrus, Pickerel, mint, Water Primrose, Japanese Iris, Horsetail, and Knot weed do well on my islands. I also put some little trailing house plant things in and they are happy now but I don’t know how they’ll winter.
I scavenged my Water Primrose, cattails, horsetail, and Pickerel from wild ponds and river back waters. Begging ads on Craigslist and freecycle got me some donated plants, and I got Mosquitofish from the county. A kind, overstocked Koi breeder gave me a great deal on some of her less beautiful ones, and the feeder goldfish I got at Walmart are doing fine. My duckweed was beautiful. Like a lush green lawn, but now it’s almost gone. I don’t know if it’s too much sun, fish eating it, my islands hogging the nutrients, or what.
I have mixed feeling about the duckweed. It was so beautiful and I was harvesting it every few days to put around the fruit trees. On the other hand it’s a lot nicer swimming without getting coated with it, inside and outside my suit. And harvesting might have gotten old after a few months. Right now though I’m spending more time in my pond than I did when it was a pool. There’s something really neat on a hot day about combining gardening and swimming. I get to stay cool and feel virtuous instead of lazy. The difference without the drying of the chlorine… I LOVE the feel of the water, even if it isn’t pretty and crystal clear YET.
I made an “artificial reef” for smaller fish to hide in by taking a roll of the blue swamp cooler pad and running baling twine in and out lengthwise down the center. Then I pulled the twine shorter to ruffle the matting and tied the ends together. It wouldn’t sink completely so I tied a rock to the baling twine to sink it. It seems like the fish enjoy it. I think it also makes a nice home for good bacteria and it’s covered with algae so it looks natural.
Great info for me and my readers. Thanks.