Bog building, also called upflow filter, eco filter, wetland filter

[Jack B. Nimble]

Just a word of caution and perhaps a good practice but it is illegal to remove water lilies up here and helps preserve nature. Most bogs would typically have only 2 inches of water above gravel in bog.

 

[Ronfire]

I see that an other KOI site has nothing good to say about bogs. Wonder why one site loves bogs and another is so negative about them.

 

[addy1]

I see that an other KOI site has nothing good to say about bogs. Wonder why one site loves bogs and another is so negative about them.

lol it is called koi keepers. My bog was trashed a lot on some other sites, they say no way could it keep a pond in good shape with either goldfish or koi.

 

[Lisak1]

I see that an other KOI site has nothing good to say about bogs. Wonder why one site loves bogs and another is so negative about them.

If you really want to get them started go ask them about putting rocks and gravel in your pond.

 

[addy1]

If you really want to get them started go ask them about putting rocks and gravel in your pond.

Bog is a dirty word there................rocks and gravel even worse.

 

[Ronfire]

I was wondering if adding an open layer below the pea gravel would help with the "plant filtering bog". It would allow the larger solids to settle out before entering the gravel. Might be counterproductive though as then it will not reach the plants. Good point is you could back flush to remove the accumulated derbies that gets past the filter screens. Bad point is you are creating pressure points holding up the gravel that could lead to a leak.

Things to think about.

 

[Lisak1]

I was wondering if adding an open layer below the pea gravel would help with the "plant filtering bog".

You're not the first one to suggest that. Technically that's what we have - we have a series of AquaBlox in the bottom of our bog. The theory is they slow the water down as it comes out of the manifold to allow for more contact between the water, gravel, and plants. I don't think debris would settle in our case though, as the manifold is below the blocks pushing water up.

 

[Ronfire]

I have a few bread trays that I think will work well to provide a space below the gravel. The holes are a little big for pea gravel size so I will add 2" of 1"rock then the pea gravel. Might add a couple of smaller pipes as well so I can blow air under to help clean it out if it is required.

 

[Ronfire]

Still planning on the 5000 gallon pond. Wondering how fine to prefilter for the bog. Leave the particle to big and it may clog up, to small and you might rob the bog of nutrients. With the bog as a low maintenance it would be good to have a prefilter to match.Is just a skimmer basket enough or would a better screen system like a VLM, RDF or Sieve

 

[Jack B. Nimble]

Agree I just have pre filter basket on intake only, no foam in it and set at mid level pond depth.

 

[addy1]

Wondering how fine to prefilter for the bog

I don't pre filter except with a leaf basket. I do not pull the water from the bottom of the pond but from about a foot or so more above the bottom. The leaf basket does not catch much, I clean it one time in the summer. The skimmer basket catches a lot more. Floating plant pieces etc.

 

[Ronfire]

Sounds like I will make a leaf basket with a 55 gallon drum with fed by a 4" bottom drain, also a T before the pump for the skimmer. Or might use 2 pumps instead in case 1 pump has a problem. With 2 pumps I could shut 1 down at night and reduce the water flow and power cost.

 

[Ronfire]

If you place rocks on top of the pea gravel in a bog do they migrate down. Thinking of having different depth of water in a bog and step it down with a row of rocks.

 

[Lisak1]

My off the top of the head answer would be yes, but if they were larger rocks, you could just keep re-setting them. I have rocks in my garden beds (small boulders, actually) that I have to reset from time to time as they will settle in the soil. If you mean rocks that are just slightly larger than the pea gravel, then you might lose them over time.

 

[Timothy]

We've had flat rocks roughly a foot in diameter (like flag stones) supporting potted plants on top of pea gravel with no issues. The silt will cover them through the course of a season, but we've experienced no evidence of settling.
The key here may be "flat".

 

[Lisak1]

The key here may be "flat".

Right - more surface area would keep them from sinking.

 

[addy1]

I have flat rocks, round rocks (not small ones) around 5ish inches or bigger that have been sitting on the pea gravel for years now. Never have had to reset the rocks.

 

[stevekind]

Hi Addy - (from my earlier thread) I *think* I've cracked it. The complication arose because , as I said in my earlier post, I wanted a stream/waterfall as well as the bog filter. I know the simplest solution would have been to have the stream running from the bog overspill to the pond - unfortunately, the shape and position of the pond makes that impractical without a major re-design of that part of the garden. So, if the stream is to feed the bog i would need some sort of sump BEFORE the bog to feed the manifold under the gravel.

My latest idea is to make the bog in the shallow part of the pond using a single, continuous liner for pond and bog and building the porous, wall as you advised, laid on top of the liner. If I then put a small pre-formed pond (about 55 gallons capacity?) into the corner of the bog, with the lip *slightly* higher than the gravel, and set the stream to discharge into that. That small pond would be linked to the distribution manifold via a bottom drain . Gravity should then push the water through the manifold.

The only issue then would be flow rates - the small pond would need to be draining at approximately the same rate as it is being fed by the stream. It occurs to me though that it wouldn't matter too much if the small pool overflowed into the gravel slightly. The alternative would be to make a non-porous wall with a spillway - that should make the flow rates less critical. In that case, I could even raise the bog vet slightly in order to form a small waterfall into the main pond - though I wouldn't want to disturb the water in the main pond too much.

Hope you follow all that. What do you think?

 

[addy1]

A single liner is the best way. We made ours with one liner.

Either would work. Mine is a continuous piece of liner that goes over the bog wall and into the bog.

If you do the small pond in the bog, I would have a whole bunch of holes coming out of it near the bottom, let as much water as possible flow out into the bog gravel down low. Some over flow is no big issue.

The main thing you want is for it to have the water go up through the plants and gravel, as much as possible. I had a top flow "bog" one time, ie water flowing over the gravel not up though. The surface of the gravel constantly clogged up with muck. I had a low drain coming out, most of the time no water came out it the water just flowed over the edge of the container.

The porous wall bog would have water flowing out into the pond but also some of the pond water would wander back though the wall. Unless you had a large flow of water out though the wall. When I was doing my "study" of bogs, tons of internet reading, the porous wall bog could also be built without water being fed into it, the pond water would wander though the wall and back out.

But imho, pushing some water flow through the gavel is the best way to get the bog doing a good filter job.

I just know when I built my pond with the bog as the only filter, a lot of people said it would never work. Glad I didn't listen, lol, my pond is a almost zero maintenance pond. The maintenance I do is yanking plants from the bog, they grow too good, grooming lilies. OW I can ignore it most of the time.

 

[stevekind]

Many thanks Addy, that is really helpful. Going to go with the preformed pond liner idea for the sump and a solid wall with an overspill for the bog. Going to spend part of today remeasuring the hole and working out the exact volume of water plus any additional volume such as the stream course. Thinking possibly of a variable flow pump depending on the numbers. Will order all the kit during the holidays and be ready to go on construction first week in January providing the ground isn't frozen. No time to waste - If the winter here is mild the frogs will be back looking for a home in February!