Bog Filtration Questions Answered

Duck Pond Bog Blog

We recently received two questions on a previous blog: BOG FILTRATION, THE PERFECT COMPLEMENT TO BIOLOGICAL FILTERS. The questions had similar answers so we are sharing them in a new blog. First question:

Have you had (or heard of) much success with using bog filters in small duck ponds? I like the idea of using both bio and bog (would help with the extra muck) but not sure if ducks would tear the bog filter’s plants up. Ideally I would set one up with 4-5 ducks in mind.

Location

Your choices will be determined by what grows best in your area. You will want to get an aggressive grower(s) in there to convert all that stuff into easy-to-prune leaves. You may need to cut the plant matter back hard, maybe more than once a year depending on your location. Figure on a complete removal with new plant material after 5 years. That will reinvigorate and refresh the appearance of the bog.

Because the roots of aggressive growers can sometimes penetrate liner, I’d cover the excavation with underlayment, set the liner then cover that with another layer of underlayment.

Bog Size

You will want a bog that’s at least 30% of the square footage of the water’s surface. That may sound excessive, but 30% is what you need for koi, and ducks are messier. Don’t hesitate to go bigger if you can. For easy maintenance, I keep my bogs shallow, but you’ll need some depth to resist the ducks. I’d probably use 8” of ¾” round gravel, which is the least costly where I live. Make sure water passes through the bed, whatever choice you make.

One last design detail that might help if you can implement it. To start the bog, I’ll set (or bury, if the bog is cut into a natural slope) a line of Eco-blox water matrix blocks 6-12” higher than water level at the head of the bog. The Eco-blox act as a settling chamber. Water entering the blocks from one side dumps all its heavy solids before passing out the top of the blocks through a layer of gravel. The water then works its way through the 8” deep gravel bed where roots remove nutrients every inch of the way back to the pond. A drain on the opposite side of the Eco-blox chamber can be opened to flush out the debris every year or two. See above drawing

The Aviary

Finally, the perimeter bog is keeping the pond in the Butterfly House crystal clear, even after 1 year with no additional filtration. Bbutterflies are easy. The photos of the pond in the Aviary, with the same system, has had issues with the ducks, geese and swans, that trifecta of vicious veggievores, devouring 80% of the bog plants.

The good news is, they only obliterated 8 of the 10 species planted. The other two, a dwarf variegated Schefflera-looking shrub and the native Purple Wandering Jew, Tradescantia pallida, are doing a pretty good job. See the rock 3’ down in the pale green water? Not bad considering there are 200 birds in there.

Consult the “Black List” of banned plants in your state before you decide on the plantings. I entered “blacklisted aquatic plants official NY” and Google returned the list for my state. Then compare that to a search for ‘Plants That Ducks Don’t Eat’ for your state. Good Luck with your duck pond!

Second Question

Hello Demi, thank you for your suggestion and answering back so quickly. Yes, Im certainly going to use 45ml epdm rubber liner. ( That was a typo). I think I got the concept. All though my existing pond had a high 3′ waterfall w/no stream.. Reading your instructions I will incorporate a stream leading into the pond. Would I still install a deep and wide stream bed with 3-5 inches of gravel in the stream or on top of the Eco-blox? (A little confused) My pump is plumbed with a 2″ Sch40 flex pipe.

So would I install a “T” at the pump with the same 2″ flex pipe but one leading up to the bio-falls filter and the other leading (connecting) to the eco-box? Once the 2″ flex pipe is connected to the inlet of the eco-box does water fill the box and passes through the rock, gravel and aquatic plants and then down into the stream? Does the Waterfall filter come out somewhere else into the stream? I get the drawing and the concept but not sure about the waterfall filter? I would still have spring flo media and filter-mat in the waterfall filter but no filter-mat in the skimmer. Correct?

Thought if you can be so kind is to draw another picture with the waterfall and bio-bog. Thanks for giving me such great advise. Can’t wait to get the pond rebuilt. But this time with a better out come. You really made some good points.

Perimeter Bog with Eco-Blox Settling Chamber

Hi again! This response required a sketch, which I’m bad at, so it took longer to reply than just text would have. To answer your questions in order: If you have the biofilter at the edge of the pond with the water flowing down a 3’ waterfall directly in front of it, keep it that way. Put the bog somewhere else along the perimeter, anywhere lush plantings will be appreciated and you can easily get to for pruning. The reason I included a stream is because I thought you had one.

Perimeter Bog

A perimeter bog like the one sketched can be placed anywhere, at any distance from the pond including right next to it, as pictured. It can also sit as high or low as you like, as long as water pumped into it will flow back into the pond. The sketch shows water flowing over the rock, but it could just as well flow around it. The bog works equally well whether you see the water coming back in as a little waterfall, or water seeps back in invisibly.

You won’t need the mat in the Skimmer because you will have effectively doubled your filtration and increased your ammonia and nitrate removal capacity. Don’t forget to add a valve to control the water going in to the bog. Don’t worry about a valve on the biofilter side. Because the bog is so much lower, the water will all go towards that lowest path of least resistance. Shutting the valve to the bog to about ¾ closed will direct a quarter of the volume into the bog, and shunt the rest of the water up to the filter.

AWG University

For more detailed information about bogs in general, check out Atlantic Water Gardens University, Natural Filtration 301: https://www.atlanticwatergardens.com/university/courses/natural-filtration-301

Building and calculating an upflow bog with EcoBlox

We recently received a question on a previous blog: BOG FILTRATION, THE PERFECT COMPLEMENT TO BIOLOGICAL FILTERS. The question was:

Do you have any additional information about building and calculating an upflow bog with EcoBlox, like shown in the graphic at the end of this blog post? You already talked a bit about the surface area of the bog compared to the pond but what about the depth and the number of blocks stacked on each other for example? 
I want to build a 15′ x 13′ pond with 3000 gallons and 9′ stream. Pond will be filled with stones and gravel, some plants and 20 goldfish (around 8″). How many blocks do I need and how do I arrange them for a fitting surface area of the filter? Do you have any recommended product to be used as tube under the blocks? Or do I have to build one myself? If so, do you have any instructions to do this?

Great question O Noble Ponderer!

Bogs are sized by surface area. 10% of the area of the pond in bog area is sufficient to consume all the nitrates a goldfish pond is likely to produce. At the other end of the scale are Koi, which need three times as much area, 30%, planted to bogs.

With 205 square feet of pond, 20 square feet of planted gravel will be sufficient. You have a 9’ stream, which simplifies matters greatly. What I would do is set one or two Eco-Blox at the top of the stream, on the existing grade on top of the stream liner. I would install two 2” or 3” flanges or bulkhead fittings on either side of the chamber thus created, down low so water enters and exits the Eco-Blox near the bottom of the block. On one side I’d attach the pipe from the pump, on the other a drain valve. Take a look at the sketch.

Water comes from the skimmer into the Eco-Blox on one side, flows up and out through a 4-6” layer of ¾-1” gravel on top planted to various low grasses or other aquatic plants, which are also planted in the gravel of the stream. The Eco-Blox under the gravel acts as a settling chamber. The outlet on the side opposite the inlet is valved. The valve is buried near the flange or bulkhead fitting, attached to a piece of pipe out to daylight somewhere.

I usually just set an 18” length of 4” pipe vertically over the valve so the handle can be accessed periodically to drain out the muck which will accumulate in the chamber. If I can’t reach the valve with my hand, I’ll slot the end of a pipe to create a wrench to turn the handle. This is necessary usually only once or twice a year.

You’ll have a great little active bog filter that uses the top of Eco-Blox chamber plus the stream to provide the necessary area for plantings. Plus a built-in settling chamber that will remove much of the suspended organic debris constantly and automatically. You may also consider adding a bottom drain to the skimmer, to pick up the rest of the debris. But that’s the subject of another post.

Bog Filtration, the perfect complement to Biological Filters

Last month my buddy Jim Chubb talked about the importance of biological filtration, why you’d want to use a biological filtration box, and how to hide a FilterFalls. In this post I’m going to talk about a complementary approach to biological filtration, the Bog Filter.

20160322_075127Bog filters are the perfect companion to biological filters, because they help complete the nitrogen cycle that begins with biofilters like the FilterFalls Jim was talking about. Biological filters harbor the bacteria that convert ammonia from fish wastes into nitrates. Bog filters take those nitrates out of the water column and convert them into plant material.

The reason this is so important is, the nitrates that result from a well-functioning biofilter are plant food, and if there are no other plants in the system, or even too few plants, those nitrates are going to feed lots and lots of algae.

That’s right. The better your biological filtration is, the more plant food is going to be created, and the more algae will grow… UNLESS there are other plants to consume those nitrates.

DSC02195Enter the Bog Filter, the perfect way to get those nitrates out of the pond water, and so, to eliminate green water and string algae. Basically, by placing desired ornamental plants in bare gravel, without sufficient soil to feed themselves, the plants take up all the available nutrients in the water and starve out the undesirable algae.

Bog Filtration is a pretty simple concept, so there are plenty of different ways to implement it. The simplest are graveled areas in or adjacent to the pond filled with bog and marginal plantings, called passive bogs because there is no active flow of water through the gravel. Active bogs use the pumping system to force water through the planted beds, and are much more effective because all the nutrients in the pond have to pass through the matted roots of the bog filter, and are removed.

There are two kinds of active bogs that differ in the direction of water flow. Downflow Bogs pull water down into the planted gravel bed, while upflow Bogs reverse the flow, pushing water up through the plant roots and out the top of the gravel bed. Because downflow bogs tend to trap sediments and clog more frequently, we’re going to talk about building upflow bogs instead.

The advantage to active upflow bogs is that they can be placed just about anywhere. Perimeter bogs, waterfall or stream bogs, even bog islands are simple to add to any existing pond, as long as they are built so the pumped water makes its way back into the pond.

One of the most effective bogs I’ve seen was built on an island in the center of an existing koi 101-7apond. A plastic grate set on cinder blocks about 6” below water level was covered with a piece of liner, then ringed with dry stacked stones to the surface. A planted gravel bed covered a 2” perforated pipe attached to a pump below the island. Water pumped into the gravel bed flowed back through the gravel and stones, stripped of all nutrients.

It doesn’t take much flow – usually one quarter of the volume of the pond per hour is sufficient. The size of the bog depends on the fish load. A goldfish pond where the fish are not fed at all might need a bog about 10% of the surface are of the pond in size. On the other hand, a pond where Koi are fed twice a day might need a bog 30% of the size of the pond.

More elaborate bogs use EcoBlox under the gravel bed to form a sediment chamber that also traps suspended solids, but that’s the subject of another post. Regardless of how you choose to install them, Bog Filters keep your pond free of algae using just beautiful plants to clear and clean pond water.

pond-free_bog

 


About the Author:
Demi is the Direct of Product Information for Atlantic Water Gardens
DEMI FORTUNA

Demi has been in water garden construction since 1986. As Atlantic’s Director of Product Information, if he’s not building water features, he’s writing or talking about them. If you have a design or construction question, he’s the one to ask.

The Importance of Biological Filtration

Over the years Pond manufactures have been working hard to give you the pond builders, a solution for the dreaded “Green Pond”. The answer? Biological Filtration! As I travel all over the US, I hear time and time again that pond builders do not use this filtration method because of the difficulties they have when it comes to camouflaging them. I am here to say, there is a way!

Before we get into the best way to disguise these black filtration boxes, let’s first talk about why they are important and why you should be using them.

beneficialbacteriaThese filtration boxes or FilterFalls, were designed to hold filter material to colonize beneficial bacteria and help filter your pond. Beneficial bacteria breaks down organic debris and fish waste, providing food for plants. Multiple pads or mats provide the oxygen rich environment for beneficial bacteria to flourish. The addition of biological media enhances beneficial bacteria growth by providing additional surface area for bacterial colonization. In turn making your pond clean, clear and a healthy eco-system.

The homeowner may still be weary about adding a filtration black box to their beautiful water feature, and educating your customer, is key. Having an up front conversation with the homeowner explaining why you are using the Filterfalls and why it is essential for the health and quality of the pond will help alleviate any concerns.

Another way to alleviate any concerns is to ensure the homeowner that they will not have to see any black box and their feature will look natural as long as it is camouflaged properly.

This will translate into a happy pond owner with fewer callback’s, saving you time and money.

Now that the customer is on board with using the FilterFalls, let’s talk about camouflage.

Line the inside of your Filter box with stone & plantings to help camouflage.

There are many ways to do this. First make sure that the area around the FilterFalls is or has been built up around the edge of the falls. Having higher ground is key to being able to easily camouflage the box. Trees, plants, rocks, logs, driftwood, floating plants are all great things to use for disguise.

Using plantings near and around your filter boxes will create more of a disguise.

Edge the inside of the FilterFalls with stones or rocks, you can also mix in some water plants for a more natural look. Logs or driftwood can be laid over top the FilterFalls for even more of a disguise.

By planting trees and bushes near your FilterFalls you can create even more of an illusion that the FilterFalls are not even there!

Another great trick is to angle the Filter box away from the viewing point so that the homeowner will not be staring directly into the filter box when they go to look at their feature. Remember, that like in nature, you never see where the water source is coming from. The same should go for the feature that you are building.

Hiding your FilterFalls

Angle the Filter box away from the viewing point so that the homeowner will not be staring directly into the filter box when they go to look at their feature.

 

If FilterFalls still aren’t your thing, Bog filtration can be used as an alternative. Check back for our next blog post on Bog Filtration by bog expert, Demi Fortuna.

 

 

 


About the Author:
Jim is the National Sales Manager for Atlantic Water Gardens.
JIM CHUBB

Jim has 26+ years of sales experience and 16+ years in the water garden industry.