Ducks Gardening

How to build a backyard pond with a DIY biofilter

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Since this is a longer, more detailed article, we’ve included a table of contents. You can quickly click the table links to jump to specific parts of the article that you’re interested in. Of course, we’ll be upset with you if you’re not interested in the whole article.

Table of Contents

Radical Duck Fanatics In Search of DIY Backyard Pond…

In case this is your first visit here, you should be forewarned that we’re duck fanatics… Radical duck evangelists who think more people (as long as they’re responsible people) should have backyard ducks.

Why? As we’ve written about elsewhere, for most people interested in raising egg-laying fowl, ducks often make a superior alternative to chickens.

One big distinction between chickens and ducks is that chickens take dust baths whereas ducks take water baths (waterfowl come by their name honestly).

“You’ve made me a decent pond, human slave.”

As such, if you’re going to raise happy, healthy ducks, you’ll need a water source for them. This can be a small kiddie pool… or it can be something more substantial. We started off with a kiddie pool, but we got tired of having to dump it out every day after our seven waterfowl quickly turned their water fowl, er foul, which then made the “duck area” of our yard into a muddy pit.

One day, The Tyrant added a new project to my “honey do list”: build a 1,000 gallon in-ground pond in the backyard for our ducks. Oh, and it needed to have a natural filtration system that used biology, rather than chemicals, to keep the water clean. Piece o’ cake. I’ll have it done before lunch, dear.

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In all fairness, my wife has a biology and clinical research background, so she’d already done the bulk of the research for me. She really just needed me for the heavy lifting. (There’s a reason her nickname is The Tyrant.)

Three ways our backyard pond changed things at Tyrant Farms

The duck village got a makeover last night. #backyardducks #ducks #ducksofinstagram

A photo posted by Tyrant Farms (@tyrantfarms) on

1. More diverse ecosystem

As you’ve probably observed, natural water features (ponds, creeks, springs, etc) are a magnet for a wide diversity of lifeforms. Since building our backyard pond, we’ve been blown away by the increase in dragonflies, frogs, salamanders, and other beneficial critters that we didn’t used to see very often. We’ve also noticed a decrease in mosquitos since ducks, frogs, salamanders, dragonfly larvae and other pond critters LOVE feasting on mosquito larvae. (Read about the other way we organically control mosquitos here.)  We have an edible organic landscape with several hundred species of food-producing plants and edible fungi, so having even more beneficial critters around to help us manage things and keep pest insect populations in check is most welcome. We now see why so many permaculturalists rave about the benefits of having garden ponds and other water features.

We rarely saw dragonflies in our garden until we built a pond. Dragonflies are voracious hunters and one of their favorite food sources is mosquitoes.

 

2. Happier humans

Humans have a deeply ingrained psychological connection to the sound of running water. On a primal level, burbling water sounds equate to an available water source, something our ancestors would have found quite reassuring before they could simply turn on a tap to get water. Any time the weather permits, The Tyrant and I finish our day relaxing next to our pond/waterfall with a beverage as our ducks dabble and bathe in their pond. A waterfall also aerates the water, providing oxygen and/or dissolved oxygen for beneficial lifeforms, including our pond’s fish, crawfish, salamanders, and perhaps most importantly: aerobic bacteria. If you’ve ever noticed a foul, sewage-like smell from a pond, a sewer, a swamp, etc. – that’s actually caused by various species of anaerobic bacteria (bacteria that don’t need oxygen to survive).   Anaerobic bacteria are often pathogenic, causing disease and illness in larger critters that ingest them. In an oxygenated environment, anaerobic bacteria can not survive or proliferate. (Side note: this is also the same reason you turn compost – turning compost introduces oxygen and encourages aerobic bacteria while discouraging anaerobic bacteria).   Yay to waterfalls and pond bubblers!

Ducklings enjoying a swim under the waterfall at Tyrant Farms.

Ducklings enjoying a swim under Tyrant Falls.

 

3. Happier, healthier ducks

Our ducks’ rigorous daily schedule usually includes about 3+ hours swimming, playing, dabbling, and cleaning themselves in their pond. Because of their pond, our ducks are much cleaner, healthier, and happier than they’d otherwise be. Since we have ducks, we were much more adamant about figuring out a natural, self-cleaning DIY pond filter system that relied on biology rather than chemicals to clean itself (e.g. a biofilter).



Planning & building your backyard pond & biofilter

I. Expectations

Building a self-cleaning backyard pond isn’t a small project, but we’d absolutely do it again because of all the benefits it’s added to our life (and our ducks’ lives). Here’s what you should expect, assuming you decide to build a 1,000+ gallon backyard pond similar to ours:

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  • Time – About 75 hours of labor (maybe you can be more efficient than us).
  • Money – Plan to invest roughly $1,500-$2,000 if you don’t have ducks and $2,000-$2,250 if you do have ducks (we recommend additional cleaning and pumping infrastructure if you have ducks, as we’ll go over shortly).
  • Outdoor Weather - Ideally, the outdoor temps will need to be above 50°F (10°C) and sunny during the time that you’re applying sealer around your waterfall or doing your plumbing joints. You can always pause the project until the right weather conditions come along.
  • Strength – If digging, lifting large rocks, and hauling heavy wheelbarrows sounds like a lot of work, get some help or consider hiring extra labor.

II. Pond Slideshow: From Start to Finish

If you’re like us, seeing pictures of something in addition to instructions is REALLY helpful. This slideshow is intended to correspond with the next DIY sections of this article. If you read something that you’re having trouble visualizing, hop back up here to the slideshow and you’ll probably find an answer!

 

III. Step By Step: How to Build a Backyard Pond With a DIY Biofilter

Since we have ducks, we needed to plan for our pumps, plumbing, and pond filter system to handle a lot of extra poo and feathers (aka “solids”). If you don’t plan to have waterfowl in your pond and you don’t think lots of leaves and other plant debris will fall into the pond throughout the year, you’ll probably do perfectly fine with a single pump and filter pond.

Whether you want to build a duck pond, a backyard meditation pond, a koi pond, a garden pond, or just a beautiful DIY pond to make your backyard extra flashy, let’s get started!

 *Note: There’s a full materials list you can use at the bottom of this article, so we won’t exhaustively list out each item in the step-by-step pond building section. 

 1. Identify the location of your pond. 

Carefully consider the location of your pond. Are there likely to be large tree roots where you’ll be digging? Underground pipes or wires? Is the area flat or sloped? How will that slope (or lack thereof) alter your pond/waterfall designs?

If you want to use our pond as a model, see the dimensions in the above slideshow and our general site plan below.

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Our initial pond site plan revised to show the second bog filter, added in the of spring 2016.

Our initial pond site plan revised to show the second bog filter, added in the of spring 2016. (click the image to view a larger version)

 2. Dig & level the pond foundation. 

Use the dimensions in the above images to measure out your pond. You can use a string, chalk, or flour to mark the outline of the pond before you start digging.

Next:

  • First tier – Once you’ve marked the outline of your pond, dig the whole thing out 7″ down (or more if you want deeper pond shallows). If you are planning to put plants in your pond, it’s a good idea to slope your shallows back just a bit towards the wall (vs. a level ledge) so that your plants & your pebbles don’t slowly slide into the center of the pond.
  • Second tier – Mark the outline of the second tier, then dig it down 12″ (or deeper if you prefer).
  • Third tier/pump hole – Mark the outline of the third tier, then dig it down another 12″.

When planning the depth of your pond, keep in mind that in the months and years ahead, you will likely need to occasionally get into the pond to check on the pump and/or temporarily remove the pump in the event of a clog. That’s why our pond is thigh deep, not waist deep. 

The different levels of our pond. (click the image to view a larger version)

 3. Sand, Fabric Underlayment, and Pond Liner 

  • Sand – Put about 1″ of sand on the flat surfaces of your pond foundation (we got 1/2 scoop from our Landscapers Supply). This helps ensure that no sharp rocks or pointy objects punch a hole in your pond liner – you do NOT want to have to trace down a hole in your liner after you’ve filled your pond.
  • Underlayment – Now you’re ready for your protective underlayment, which prevents abrasion & punctures, further extending the life of your liner. There are different things you can use here. We had some old landscape fabric sitting around, so we used that. The landscape fabric came in a long roll, making it difficult to universally cover the tiered pool foundation, as you can see in the slideshow. That’s why we’d recommend using this this 15′ x 20′ geotextile underlayment instead.
  • Liner – Now comes the liner. We did a lot of research here, and we recommend using this Firestone 45 mil. EPDM, 15′ x 20′. It’s a UV-resistant, highly flexible yet stable waterproofing membrane with a proven performance history in exposed applications – equally tolerating extreme cold and heat while maintaing its flexibility/not tearing. The liner is also safe for exposure to wildlife and aquatic plants, which is important to us given that we’re owned by ducks. The liner fit snuggly into the contours of our pond and the black color allows any exposed surfaces to blend in with our rocks. Some people we read about opted for a PVC liner – don’t do it! You’ll likely end up with cracked liner and water leaks within a couple years, whereas the 45 mil. Firestone will last for 20+ years (it has a 20 year manufacturer warranty).  
Our girls swimming on a snowy night.

Our girls swimming on a snowy night.

 4. Pebbles & Rocks 

Now it’s time to start making your backyard pond beautiful! Build up, tier by tier, from the bottom of your pond to the top. Let us repeat that: do not start from the top and work down or you could end up with stretched liner or rock problems.

Want to calculate how many large rocks and pebbles/gravel you’ll need? Here’s a calculator.

Place large landscaping rocks along the sides/walls of the third tier of your pond. Fill in the flat surfaces with 2″ of river pebbles and an occasional large flat rock to add stability and keep the pebbles from shifting too much. Repeat, tier by tier.

*We put a large flat rock in the center of the bottom tier/hole on our pond to provide a base for our pump and keep the pump off the very bottom of the pond (this helps keep the pump from getting clogged). 

On the outside lip of our pond, we used concrete edgers/bricks covered with our native red clay to provide a smooth, solid lip that was level all the way around the pool AND to raise the level of the liner up ABOVE ground level (that way, full pond = ground level or slightly below). The underlayment went over this lip, then the liner went on top. Large landscape rocks were then placed on top to hold the liner down and hide it. The liner extended out about 6-8″ past the lip to allow for any settling or future pond expansions/alterations. (You can also easily seam together the liner with special pond liner adhesive.) All around the outside of our pool we put down wood chip mulch.

Double check to make sure every tier of rocks is solid and stable – no shifting, slipping, or sliding rocks. Everything nice and snug.

We have Welsh Harlequin ducks, a heritage breed that makes great pets and egg layers. They're bred from Mallards, which are

We have Welsh Harlequin ducks, a heritage breed that makes great pets and egg layers. They’re bred from Mallards, which are “dabblers.” Dabbling ducks tip underwater to forage, while keeping their butts and feet on the surface. Our ducks will do short dives for fun, but they’re not technically “diving” ducks, which can swim and hunt underwater for over a minute at a time.

 5. Skippy BioFilter, Plumbing, Pumps 

Once your rocks and pebbles are all in place, it’s time to let your jeans slip down partially off your behind to show off your inner plumber. (Actually, don’t do that.)

1. Set Filter Pond – First, get your filter pond placed. To prevent the filter pond from sinking/settling, you’ll want to really tamp down the foundation soil underneath it, then add about 2″ of gravel/sand mix, then about 1″ of sand over top of the gravel to prevent the gravel from roughing up and potentially puncturing the underside of the filter pond (alternately you could use concrete pavers or pour a concrete pad below your freeze line).

We recommend using at least a 50 gallon+ filter pond. This is the one we wished we’d used on our first filter pond (we used it later on a second filter/bog pond), but we used the old pool we already had instead. A 50 gallon filter pond should be more than adequate to clean a ~1,000 gallon pond IF you don’t have ducks – we added a second 50 gallon filter pond a year later since we have seven ducks.

The exact ratio of filter pond to main pond is hard to determine. There are probably too many potential factors to come up with a precise ratio that works for every scenario. For instance, if you have ducks, you’re going to want to have a much higher filter-to-pond ratio than someone who just has a couple of fish in their pond. One fact remains: you can’t have too much filter pond, but you can certainly have too little – so err on the side of too much biofilter/filter pond, especially if you have waterfowl.  

2. Plumb the Pond - Position your pump on the rock in the center of your pump hole. We highly recommend the Laguna 2900 Max-Flow pump – especially if you have ducks. You want a pump that can handle solids and one that has enough power to turn your pond water over 2-4 times per hour (calculations here). The Laguna is also extremely energy efficient. Once your pump is positioned, measure and sketch out the lengths of PVC pipe and joints you’re going to need to run pipe from your pump into the base of your filter pond. (Again, the full list of plumbing supplies we used is at the bottom of this article – but the exact joints and lengths of pipe needed may vary depending on where you locate your filter pond.)

Do NOT seal any plumbing joints until you’re confident everything is sized and fitted correctly. Once you’ve linked it all together and everything fits, seal your plumbing joints one by one, locking everything into place.

3. Add Biofilter Media – Place protective framing over the inflow in the bottom of your filter pond to make sure the pipes don’t get clogged with filter media when you unplug your pump (due to gravity, the pump sucks back out when turned off since the filter pond is higher – unless you plumb in a cut off valve at the top).

Next, put your filter media in a wheelbarrow or large tupperware. (Filter media options are listed at the bottom of the article, but we recommend natural hogs hair air filtration rolls, especially if you’re going to have ducks in the pond.) Dampen the filter media with a hose. Now, you’re going to want to start filling your filter pond with your filter media, but you’re going to inoculate each layer of media material with this beneficial pond bacteria as you fill the filter pond – wear rubber gloves for this. This is the primary bacteria that’s going to clean the water in your pond and its home is going to largely be in your filter media.

Fill the filter pond to the top with your bacteria-inoculated filter media. This setup is called a skippy biofilter – you can geek out on the details here if you’d like.

 6. Build Your Waterfall 

It might seem counterintuitive, but we built our waterfall last. We wanted to have all of our plumbing and the filter pond in place before we put in the rocks that hide and support it.

There’s no single formula for building a waterfall, and yours will be unique because your rocks are unique. Some people concrete their foundations in, which is perfectly fine – but that doesn’t allow you to easily change things/iterate later, which is why we went a different route. We simply built up a foundation with gravel, sand, and stone, then put pond liner under our final top-level rocks going down the waterfall in order to prevent water from escaping out of the system via the waterfall.

Since we’d never built a waterfall before, we looked at hundreds of photos of waterfalls online for inspiration. We’d recommend you do the same.

You’ll also need to cut an opening in the siding of your filter pond, and use a scrap of pond liner and “fish-safe” silicone sealant to attach the liner to the inside of your filter pond. The liner will need to extend out of the filter pond and onto your first waterfall rock to prevent water from leaking out behind your waterfall.

 7. Testing, Testing, 1, 2, 3 

Show time!

Fill up the pond with water – ideally you can use a dechlorinator to filter the chlorine out of the water you fill your pond with since chlorine can kill beneficial bacteria.

It’s a good idea to take a close look at your rock pond walls as the water fills around them to make sure they’re not settling or moving too much, thus requiring you to reposition them.

Once your pond is full, plug your pump cord into a yard outlet (we’ve been using this Yard Master 6-Outlet power stake for three years). It’s a magical thing to watch your backyard pond come to life for the first time!

If your water is muddy and turbid for the first 7-14 days after you fill it, don’t despair! That’s normal. It will take a bit of time for your filters to kick into full gear and your pond to clear up.

Also, as your pond is filling and for the next 24-48 hours after it’s full, keep a close eye out for any signs of leaks. Is the ground wet where it shouldn’t be? Is the pond level dropping? If so, there’s a good chance you have a leak, and 9/10 times that leak is happening somewhere in your waterfall and can be easily fixed by rearranging a rock or pond liner.

Depending on the time of year when you build your pond, you’ll probably want to add a second type of pond-cleaning bacteria to your water once the pond is full – either a warm water of cold water bacteria (see materials list below for links).

Congratulations, you’re now the proud new owner of a gorgeous backyard pond that you built yourself!

Happy ducks splashing and frolicking.

Happy ducks splashing and frolicking.

IV. Ongoing Maintenance & Alterations To Your Backyard Pond

Ongoing maintenance on your pond will be minimal if you don’t have ducks. The fewer ducks you have, the less maintenance your pond will require.

Given that we have seven ducks, we decided that our single biofilter pond needed a friend, so we added a second 50 gallon filter bog with a waterfall that cascades into the back of the first filter pond. The general rule is you want your bog/filter portion of your system to be at least 20% of your pond; ex: 100 sq ft pond surface would need 10-20 sq ft bog/filter system. (You can read more about that here if you’re interested.)

We also ended up adding a second waterfall off of our original filter pond to add additional waterflow/aeration to the near side of our pond. You can see that project pictured below:

Due to seven ducks using the pond for several hours per day plus a large oak tree dropping debris into the pond regularly, we decided to add a second pump and filter plus an additional/secondary waterfall to increase aeration.

Due to seven ducks using the pond for several hours per day plus a large oak tree dropping debris into the pond regularly, we decided to add a second pump and filter, plus an additional/secondary waterfall to increase aeration. Svetlana the Duck makes a great foreman.

Additionally, to get even more oxygen into our pond to keep Sid Fishest and his fish family (our four pond fish) happy, we got two of these small aerators. More oxygen into your pond = healthier pond water. We do clean our filter media 1-2 times per year as-needed, but without ducks you should rarely (some people say never) have to clean your filter media – that’s one of the neat things about the skippy biofilter system.

Using the test strips in our materials list below, we test our pond water periodically throughout the year and it has yet to measure anything less than ideal.

Pond Maintenance Schedule

If you don’t have ducks, here’s what a normal ongoing pond maintenance schedule might look like:

  • Spring
    • Check pond water quality with test strips (here are the ones we use);
      • if high nitrate levels, add seasonally-appropriate beneficial bacteria, then test water again a week later.
    • IF waterfall has slowed due to debris clogging it, unplug the pump. The water reversal will usually dislodge whatever is in the pump impeller; if not, you’ll need to hop in, disconnect the pump, pop off the top and remove the clog manually.
  • Summer
    • Same as spring.
  • Fall
    • Same as spring, plus remove fall leaves by hand or with a net so they don’t clog your pump.
  • Winter
    • Same as spring, but we recommend getting a pond de-icer if you live in a cold area. We live in Greenville, SC (Ag Zone 7B) – not exactly known for frigid temps – but our pond will still freeze over on really cold winter nights. After breaking apart and removing the ice with our numb hands enough times, we finally decided to get this floating de-icer. It’s kept our pond completely ice-free down into single digit temps, which makes us and our ducks very happy.

 Complete Materials List For Backyard Pond 

Stones, Pebbles, Gravel, Sand

Easily found at local landscape supply companies.

  • 2-4,000 lbs rock (1-2 pallets)
  • 1/2 scoop sand
  • 1/2 scoop river pebbles
  • 1/2 scoop gravel

The Skippy Biofilter

(Complete assembly instructions here)
Materials List:

  • 50 gallon tub
  • 1 – length of 1 1/2 inch PVC pipe (1 inch PVC pipe for the Mini-Me Filter).
  • 1 – PVC tee.
  • 3 – PVC elbows.
  • 1 – 1 1/2 inch to 1 1/4 inch threaded nipple reducer (For the Mini-Me, use an appropriate fitting to attach the hose coming from the pump).
  • 1 – 4 inch closet flange (For the MiniMe, use a 2 inch floor shower drain).
  • 1 – plastic egg crate style overhead 2×4 light grate (or something similar). You can find these in the ceiling tile section of Home Depot or Lowes or other hardware store. It’s a ceiling light grate panel.
  • 4 – 1/4 inch by 1 1/2 inch bolt, nut and washer combinations (bolts not needed for the Mini-Me Filter).
  • Filter medium – we used a combination of coarse (reusable air filters, cut into rectangles) & fine (steel wool pads) for our filter medium
    • (*Recommended) Hogs Hair Air Filtration Roll – 20″ x 360″ – link
    • Heavy Duty Scouring Pads, 6″x4″, 2 Packs, 20cts – link
    • Scotch Brite Heavy Duty Industrial Size Scouring Pads (20 pack) – link
  • Bacteria inoculant for filter media 

Pumps & Aerators:

Pond Making Materials: 

Miscellaneous:

DIY/How To: Build a backyard pond with a self-cleaning biofilter

Questions? Ask away in the comments section below!

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  • http://www.pondpro2000.com Latoya Saum

    Lovely post I like it particularly you are advising with respect to all basic issue to be thought in conspiring and setting up of a scene. For pond Pondpro2000 would one sure solution of leaks.

  • Dave

    Great article but the pics that you have here are really small is there anyway we can see normal size. 150 x 150 really doesnt help understand whats going on.

    • Dave

      Does anyone actually look at this?

    • http://www.tyrantfarms.com/ Aaron von Frank

      Dave, sorry for the delayed response! For some reason, I’m not getting comment notification emails despite my settings showing that I should be. The native slideshow function on our site is also a little wonky, but you should be able to click the pictures now to enlarge them, then click back on your browser to return to the images. Apologies and hope that helps!

  • GCEMSPete

    Hello! How often are you having to clean out the biofilter?

    • https://www.growjourney.com Aaron von Frank

      Hi! It depends on whether you have waterfowl or not. If you don’t have ducks pooping and molting feathers into your backyard pond, you might not ever have to clean the biofilters (although you might have to replace them if/when they biodegrade). However, we have seven ducks that spend a good portion of their lives in our small pond, so we have to clean the “solids” out of our filters about twice a year just to make sure the water stays in ideal shape. It’s not the most pleasant job in the world but our plants and compost benefit greatly from the byproduct. :P

      • GCEMSPete

        We have seven khaki campbells and I was cleaning out our old pond which was just a kiddie pool several times a week. Thanks for the response! I have been following your plans and we are almost done, just have to finish the rocks. Any other suggestions?

        • https://www.growjourney.com Aaron von Frank

          Sounds like you’re about to have some very happy ducks! You’re going to get a good laugh out of how happy your flock is when you first fill up the pond. They’ll be in there constantly, cleaning, diving, dabbling, etc. Ours still love their pond as much as the day they got it but they’re asking for an expansion or a second pond. Spoiled birds. It’s never enough.

          As for other suggestions, sounds like you’re right on track. If all you have left is rocks, you’re close to the finish line. Did you have any specific questions about construction, design, or plumbing? Happy to help you as you finish up.

          • GCEMSPete

            So my pond is pretty much complete, just have to put the hogs hair material in the biofilter. Did you do layers of scrubber pads in between layers of hogs hair?

          • https://www.growjourney.com Aaron von Frank

            Ideally, you can layer it based on porosity: filter material that catches largest materials goes on the bottom and filters that catch the smallest material goes on top. Depending on what you’ve got there, that’s probably going to mean your hogs hair filters are going to go on the bottom and your scrubber pads are going to go on top. Does that make sense?