Veggie or Bog filter?

[Waterbug]

Oh there's no data at all on bogs, size vs performance. I've never heard of anyone ever testing any kind of parameters related to a bog. It's a kind of filter that's used by people who don't test and measure stuff.

So generally what people do, to sound like experts, is to say something like a bog should be X% of the pond. Or "mine is X big and I have perfect water because it looks good to me".

Testing and measuring filter performance is only done by people who really need a filter to do something. Most ponds go clear without a bog. But every pond that goes clear AND has a bog the bog gets full credit. If the pond isn't clear the bog is said to not be big enough, even though "big enough" is never actually defined.

There is no advantage to vertical vs horizontal space as far as anyone has shown. As for theories I can come up with several for both cases.

My advice...build it as big as you'd like it to be.

If you can have the bog outflow go into even a short stream before going into the pond that would be a plus. You have to expect the water coming out to be low O2 and high bad gases, so some gas exchange before the pond would be nice. In a pond with a few small fish this is generally no big deal. But higher O2 is considered a plus.

Plus even a short shallow stream is a proven good bio filter and gas exchange and possible could grow macroalgae which may kill green water algae. Some of the best bio filters are based on streams.

 

[bean6924]

Thanks Waterbug. I should have been clearer in my post. sorry.

I'm thinking of more traditional filtration now for my pond. I'm thinking of of a diy system similar to this -
http://www.earthangroup.com.au/diy-b...l-flow-filter/

But, I would use two 30 gallon drums in-line (one for for mechanical / one for biological). Both below pond level and gravity fed. This would clean a 1000 gallon goldfish pond. I'm wondering if 30 gallons good enough? I'm thinking this will provide more filtration than a bog, easier to clean, etc. But, I've seen most use 55 gallon drums.

 

[Waterbug]

Oh I see now. By "bog" you mean a filter that has absolutely nothing to do with a bog and in way whatsoever.

Yeah, the 30 gal will be perfect.

 

[HARO]

I live about 3/4 of a mile from a bog. Not a gravel pit with an upflow of water, but a REAL bog! Lord knows how long it's been in existance, but I'm sure it's been several thousand years. Currently it is about ten acres in size, and the sphagnum moss it contains feels like it's about 20' deep when you walk over it. Rubber boots are a good idea, for although it contains no visible water, your feet WILL get wet. The surface of this bog is covered with cattails, sedges, various reeds, cotton grass, pink ladies' slippers and many other plants. Scrubby willows form a taller ring of vegetation around it, while cedars are starting to close in around the perimeter. Does anyone really believe that this can be replicated in a corner of a suburban back yard? Let's call these structures what they are... gravel filters, vegetative filters, or whatever, but they are NOT bogs, any more than a backyard pond is an ocean!
John

 

[Catfishnut]

Waterbug,

To clarify some of my points regarding bogs:

I can cite no reference where I gathered the notion of a bog except for "nature" itself and according to the real definition you linked to, what I have seen in nature is NOT a true bog. Locally here, along and within the Platte River of Nebraska and in the sandhills of Nebraska there are large expanses of wetlands or "marshes". The soil composition is primarily sand and gravel with vegetation growing in very wet conditions. The "wet" could be anything from a slow trickle flow through the sand and gravel to even small rivulettees meandering between the vegetation with lots of springs and pools and the water disappears underground for a distance and then reemerges as a spring. At the outlet of the "bog" (or should I call it a "marsh"?), the water comes out pure and clear. This was my definition of a natural bog, and it seemed to reflect the very aspect of what everyone was doing or creating as a "bog filter" for their ponds.

Rejuvenation of these marshes in nature came from the change of seasons mostly. Winter freezes and floods would scour them out and replace them with new material or at least turn the old over and stir it up. The landscape of the marsh would become totally changed, but it would still be there. On the river (Platte River) such marshes would typically be found on some of the islands scattered all throughout the river valley. These would come and go over time. Major ice-jam floods would either erase them or create new ones. High water levels would tend to purge them like backflushing a slow-sand filter. If the water doesn't get high or flood enough or if there aren't any ice-jam floods and maybe there is a drought, the marsh slowly closes up. The short vegetation gives way to trees and vines and eventually the marsh is gone completely. But, several years down the road, nature reclaims her rite and scours out a new streambed that will eventually become a boggy marsh.

I have witnessed these "marshes" all my life and I was fascinated by them. When I started reading about "bog" filters here and read some of the descriptions, I branded that concept with my past experiences in nature from my local environment. I studied these systems (not scientifically, just observing and learning and enjoying) and I see that they really work very well! I therefore believe that these "bog" filter systems are highly beneficial and effective for pond owners, but I stress the importance of the "size" of the bog, the materials used and the design.

The term "synthetic" to me just means to emulate what you interpret from nature. You cannot truly duplicate it, but you can give it a fair shot, but it will not be a BOG. I guess that is just a quaint term that is easy to use and remember, but you are correct, it is a misnomer.

Gordy

 

[Waterbug]

Yes, I see. Many different things.

Bog's aren't required to have plants, but many do. Most of the benefits from bogs are bacteria related and settling of suspended particles. Plants have advantages too, primary being they look great. A bog with a lot of plants would be more of a veggie filter. Here's three general ways I set up a bog. The actual final design is almost ways going to be a combination of these.

Adding plants to a winding bog is a bit of an issue because the plants can block off the water flow. Normally not a big deal because in those spots the water flows over the surface to get over the plant's root ball. But generally a winding bog isn't packed with plants. The primary use of a winding bog is to increase the chance of the bog stopping green water without using a UV.

On the other end a Veggie bog is primarily for growing plants. While these can certainly stop green water they're less likely to. Of course if you add a UV then green water isn't an issue. And for all of these bogs, a UV can normally be turned off after a few weeks and the bog, stream and pond will keep the water clear for months.

The Winding Veggie is something in between. Lot's of ways to configure these: as shown, half Veggie and half winding Bog, etc. For the Winding Veggie runs you increase the width to about 18-36".

 

[Catfishnut]

WB,

Your third depiction of the VEGGIE system is most akin to what I see out on the river - on the islands. Maybe a little bit of a cross between the 2nd (winding) and the 3rd. The "skimmer" might be a small beaver dam in a meandering stream just a few feet across, or a more random natural obstruction like a fallen tree / log jam, some ancient glacial till deposits or uplifted / misplaced bedrock. Down below the dam the water would be very shallow and wind through the vegetation. Plants such as cattails, marsh reeds and plants looking like arrow plants and thick mossy algae would arise. The landscape would also define how the water meanders through this "garden". It is actually quite beautiful to view and I see how it can filter and purify the water in many ways.

What I am seeing out on the river is probably moreso a combination of a settling tank + mechanical sediment filter + slow sand bio-filter + upflow fluidized bed sand filter + aquaponics/veggie filter + maybe a minor UV system just from sunlight.

Gordy