Can a bog filter be submerged 20" underwater?

[Hop-frog]

I am currently constructing a 20,000 or so gallon backyard pond, the design is a complete circle in design.

After learning about bog filters, I considered that a place to install is to extend the deep end and bury the outpout pipe from the pond pump underground so it feeds into an underground cavity, created by milk crates, then covered in various layers in rocks. The problem with the design is the top layer of rocks still falls 20" below water level. Because of the symetrical design, I can't change the appearance much by having an area of shallow water.

Can a bog filter still work when fully submerged?



~~~~~~~~~~~~~~~~ <--water level

<--20 inches of water

.................................<--small pebbles
.................................<--larger pebbles
[][][][][][][][][][][][][][]<--milk crates creating a cave, the output of pond pump feeds under there

 

[Mmathis]

Hello and welcome!

I’m not sure you are asking the question it sounds like you are asking, but here goes.....

A bog can be almost any depth, but are you talking about a space specifically cordoned off to serve as the bog, or are you talking about a section of the pond that is filled with milk crates and rock? It almost sounds like you are talking about the latter — correct me if I misunderstand.

A bog is usually a part of the pond that is somewhat walled off from the rest of the pond, so you could think of it as being a pond within a pond. Water from the pond proper is pumped into the bog (usually an up flow system: water flows to the bottom and percolates up the gravel bed which is filled with plants. You can make the bog be like a separate little pond, separated by dirt and liner. Or, you can build a wall within the pond (cinder block). I had one that I called a “satellite bog,” that was physically removed from the pond, but the water was pumped between the 2.

There are many, many ways to build a bog. @addy1 has a “bog building” thread that explains the different shapes or positions within the pond: one way is to have the bog encircle the pond.

 

[j.w]

@Hop-frog

 

[brokensword]

I am currently constructing a 20,000 or so gallon backyard pond, the design is a complete circle in design.

After learning about bog filters, I considered that a place to install is to extend the deep end and bury the outpout pipe from the pond pump underground so it feeds into an underground cavity, created by milk crates, then covered in various layers in rocks. The problem with the design is the top layer of rocks still falls 20" below water level. Because of the symetrical design, I can't change the appearance much by having an area of shallow water.


Can a bog filter still work when fully submerged?



~~~~~~~~~~~~~~~~ <--water level

<--20 inches of water

.................................<--small pebbles
.................................<--larger pebbles
[][][][][][][][][][][][][][]<--milk crates creating a cave, the output of pond pump feeds under there

a bog with a water level lower than the pond can work but you'll have to pump the 'rising water' from the surface BACK to your pond as you'll not have gravity to help you. Doesn't matter if inside or outside your pond. I'd suggest you make your bog higher than your pond by whatever means (whether inside the pond proper or outside as most of us have it) so you don't have as many moving parts to maintain.


If you go with your idea, make sure the water being pumped to the pond from your bog cannot back siphon. If you pump into some sort of weir/tube outlet, and let it pour back into your pond, you'll be okay.

An upflow wetlands filter, what most here call a bog, is something that you basically build and barely maintain; usually just monitoring the plant growth.

 

[Jhn]

The short answer is no. If I am understanding your idea correctly, as Mathis said it sounds like you are just going to stick milk crates in a section of your main pond and bury it in graduated size rocks with the outlet from the pump feeding into the milk crate void. it is more of just a submerged planting bed, while the rock/gravel will still create more Specific Surface Area for nitrifying bacteria to colonize. The water won’t be forced up through the gravel, unless the bog area is walled off somehow, rocks aren’t going to do it, will need to be some type of membrane/cinderblock wall. Also, if you don’t create some type of output grid under those milk crates the water is going to just upflow through the gravel and rock pretty much right where the pump outflow pipe is located. You will also be severely limited on plant choice ie lilies and submerged oxygenators.

What you are doing sounds like a reverse under gravel filter, just pumping water up through gravel over a plenum on the pond bottom.If aesthetics/Symmetry is what is preventing you from adding an actual upflow bog, I like @Mmathis idea of encircling the pond with an upflow bog that just spills back into the pond.

 

[GBBUDD]

i know Aquascapes has built one. who what how is the unknown i did a quick sear ch for the video i saw but no luck so you'll have to do the leg work. Ohio Fish Rescue has a indoor pool and that indoor pool has a bog at the bottom of the pool how they did it i do not remember. but i believe it had aquablocks and the water is always crystal clear in every video i have ever seen . good luck

 

[Jhn]

i know Aquascapes has built one. who what how is the unknown i did a quick sear ch for the video i saw but no luck so you'll have to do the leg work. Ohio Fish Rescue has a indoor pool and that indoor pool has a bog at the bottom of the pool how they did it i do not remember. but i believe it had aquablocks and the water is always crystal clear in every video i have ever seen . good luck

Interesting never heard of that, heard of the suction grids or even a reverse one were it is pumping water up through the grid and gravel. Not sure how they call that setup at the pond bottoms a bog/wetland filter, since by definition a bog or wetland is just a soft, wet, swampy area.

 

[GBBUDD]

I would imagine a manafold system set on the bottom just like a bog a layer or gravel to flush up the bottom. place the aquablocks and throw down the pea stone . I would be concerned about Lack of 02 but obveously they did something to make it work as they have some huge fish in the pool . And i could be wrong not sure what they did here but there is a second video i saw that talked more about what they did . likeIi said before good luck

 

[Hop-frog]

Just to bring some clarity to my post, the pond is quite similar to this, with two circles, the first a shallow area, then inside a deep area for fish to hide or go during the winter. The difference is my pond is about 5x larger. And unlike this pool, which has a shallow area around serving like what I think is a bog filter, I had to build a wall around it to keep out outside flooding, which means the "shallow" area in my pool is 20" deep. I wanted to build the bog filter in a 15 ft section buried in the shallow area, but it seems from the answers the bog wouldn't function. Yes, as one person pointed out, what I'm building resembles an underground filter found in a fish tank, just at a much larger scale.

 

[GBBUDD]

If you gave the room build a body outside the pool/pond there are so many flowering plants you just can't have without a bog. And to have it with a waterfall into the pond or dropping into a stream to a waterfall into the pool adds so much visual stimulation. Ask anyone here how much time they spend happily watching the falls and streams and fish. Most would like to move therebednext to the pond. Ok maybe not the bed but definately the lazyboy recliner.

 

[Lisak1]

DEFINITELY the LazyBoy. And I look at those outdoor chaise/bed things longingly, thinking "if only I had the space...".

I have seen ponds built where the bog is "in" the pond, but there's a wall providing separation under the water. So if you look at the pond, it appears to be one body of water with one portion being more shallow and planted. If you search YouTube for swim ponds (mainly in Australia at the time I was looking at them) you may be able to find something that you could work with.

 

[GBBUDD]

DEFINITELY the LazyBoy. And I look at those outdoor chaise/bed things longingly, thinking "if only I had the space...".

I have seen ponds built where the bog is "in" the pond, but there's a wall providing separation under the water. So if you look at the pond, it appears to be one body of water with one portion being more shallow and planted. If you search YouTube for swim ponds (mainly in Australia at the time I was looking at them) you may be able to find something that you could work with.

Agree with the exception of you pump the water there but you loose the opportunity fora waterfall to me waterfall are an equal to fish as far as entertaining

 

[Lisak1]

you loose the opportunity fora waterfall

True true... but you could always add a waterfall that's separately plumbed, no?

Here's an example of what I was suggesting:

The wetland filter surrounds the pond, but the water from the pond is higher than the edge of the bog.

 

[GBBUDD]

I did a lot of research into that design particularly due to the air lift and cutting power consumption way down. Not that you can't still pump to the bottom of the bog and let the water work it's own way out but i did see two of the first designs had not worked so well. and then there were others that were very mature and seemed like a real deal pond i preferred the clear waters over tannin. i saw a latter video of this builder where he had ripped the pond apart and started over

 

[Lisak1]

Interesting! I watched so many of these videos early on and got really intrigued by the idea of the in-pond bog. It didn't work out space wise for us, though, but I do like the look. Like you said - looks so natural. I saw one huge project where they were using a bog filter on a public swimming pool. I'll have to follow up and see how that worked out. People were really questioning if that would be enough filtration to keep the water safe for swimming with a large number of people.