Which is more important to the success of a bog filter? Volume or surface area?

[Hop-frog]

Does anyone know which is the more important factor to measure if a bog filter is big enough and will be more benefital for cleaning? Should I work to make sure I maximize the available volume, depth, length, and height of the bog, or focus on expanding the surface area, if that means maybe some of the parts is not so deep?

 

[TheFishGuy]

well surface area is kind of related to volume, if we are talking about surface area the beneficial bacteria has to colonize. I would say as far as what you are probably talking about, surface area, because you would have more places for plants to grow, and it may be less likely to clog.

There's is a certain depth that is good as it does give you a decent amount of space for plants to grow, while still allowing it to be deep enough to actually plant them ( and of course have massive amounts of beneficial bacteria )

what that depth is? you decide! though I would say 12" is decent minimum, but 18 or 24 might be ideal.

and almost everyone on here does know more about bog filtration than me, so I would wait for @addy1 and @poconojoe and then maybe @GBBUDD and @Lisak1 to pop in here for the real deal. Oh and @Mmathis knows everything, but I am sure they will be here in no time.

( BTW that was just to name a few, literally everyone on here has a bog )

 

[GBBUDD]

While i still fell bogs are in the infancy as it really hasn't been proved you must make your bog this way and not that. The basic principle is
1. Give bacteria a place to grow.
2. At least a foot is the recommended minimum in depth for a pea stone bog. " i'd go for 18 to 24 like mentioned above to allow there to be an area thats not completely root bound by deeper rooted plants.
3. More surface more area for plants
4. Depth is also proven here not to be so critical as addy 's is around 30 " deep and LONG and 4.5 ' with no aqua blocks while I have a very deep aqua block settling chamber. Both ponds are clear both have plants growing where they have to be thinned by the arm full.
5. i would lean toward the surface area recommended size is 30% of the ponds surface area along with some depth 18 -24" Addy used i believe 3/8 pea stone exclusively while i have almost every size from 8" to 3/8 in layers. Round river rock is the recommended or pea stone I have only seen one person come on the site saying the bog failed them but the pictures they showed left more questions then answers My build can be found in the blue text below this text

 

[brokensword]

GB covered most of it, I'll add;

--use a lot of shallow rooted fast growing plants (parrots feather, creeping jenny, pennywort, forget-me-nots), and not all deep rooted/heavy mass rooted plants like iris and taro. You WANT that aggressive root growth as that facilitates better nitrate uptake. You'll thin more often but that's your proof the bog is working re the plant area.

--don't use any 'sharp edged' stone as it'll pack and not remain loose like rounded stone. River rock, pea gravel, cobble stone all are smooth, round edged.

--not all provide this but I think it's a good idea; some sort of cleanout in which you'd drop a pump so you can backflush the bog. Not necessary but if you're starting new, it's not a hard feature to establish. Search the bog threads here and absorb what others have done. The primary reason we do bogs is because it keeps the water very clear and is very low maintenance, if at all. Thinning plants on occasion is about the most you'll do once the bog is up and running.

Like GB, I have mutli-layers of rock; 3 layers starting with 8" then 2" then pea gravel. My bog is about 3' wide x 20' long x 36" deep.

 

[addy1]

Mine is deep, 2.5 feet, long, 26 or so feet, 4.5 feet wide, no clean out, nothing but two pvc pipes with slashes, nothing but pea gravel and plants and it does great. Running for 10 years now.

 

[Lisak1]

If I had to choose, I'd pick surface area as that gives you both more room for gravel as well as more room for plants. However, the only real limit to your bog size IS surface area - the depth is completely dependent on how far you want to dig!

 

[Mmathis]

I know everything, so no comment.

 

[poconojoe]

I know everything, so no comment.

Ha! You made me smile!

 

[poconojoe]

All good info above.

The general consensus for the simple type bog (no aqua blocks, centipede or snorkel) design is at least 12" of gravel, but some have it deeper.

To size your bog:
Your bog surface area should be at least 30% of your pond surface area.

Mine is very slightly over 30% and it's 12" deep. It keeps my very overpopulated pond crystal clear.

I used smooth river stone. I got it at a local garden center/nursery. At the time, the local quarry/mason supply was closed due to Covid.

My water was a constant solid green before adding the bog. I previously had two pressure filters and a UV light. My water was never clear and I was constantly cleaning filter media.
Now I can see a grain of sand down 3 feet. I saw baby fish I didn't know were there. I found a submerged plant I didn't know was there. The water looks like you could drink it now! The bog is my only filter now.

I have two 2" manifold pipes buried under the gravel with slits cut in them. The ends of the pipes turn up and end at the surface of the gravel. There's a screw-in cap on them for quick flushing if needed. I turn off the pump, open one cap, then turn the pump back on. The black water shoots out for a few seconds, then runs clear. I then turn off the pump and do the second one. I shoot the dirty nutrient full water into a garden for fertilizer.

Build your bog walls 6"-8" higher than the gravel surface just in case the water rises in the future for some reason.

Try to keep all your plumbing within the pond and bog. This way, if a leak occurs, it will not leak out of the pond/bog system.

Here's my bog add-on build:

My add-on bog build

I finally did it! I joined the bog club! The bog is approximately 14 feet by 5 feet and about 12 inches deep. I know my 1600+ gallon pond has been overpopulated due to my fish reproductive rates! Last year the water never cleared up to my liking. I figured my two pressure filters and my...

www.gardenpondforum.com

 

[poconojoe]

Just as another note...
It's funny, you can read a lot online about bogs and get conflicting opinions on almost all aspects of building one.
The thing is, many people here have broken those so-called rules as far as depth, gravel size and gravel type.
I believe there's a lot of leeway. For example, I read that any deeper than 12" was bad. They say the beneficial bacteria can't live that deep due to lack of oxygen. Meanwhile, many members here have way deeper bogs and they are doing great.
So, what I'm saying is, there's a lot of wiggle room. Make it simple and properly sized in proportion to the pond, and you'll be good.

 

[addy1]

It's funny, you can read a lot online about bogs and get conflicting opinions on almost all aspects of building one.

lol when I built mine and my pond, bogs were a big NO NO, it would never work worthless don't do it. I studied monster pond build forums, added what I had already done on a small scale and did a bog any way. Love the sucker, the pond is nothing to care for.

 

[poconojoe]

lol when I built mine and my pond, bogs were a big NO NO, it would never work worthless don't do it. I studied monster pond build forums, added what I had already done on a small scale and did a bog any way. Love the sucker, the pond is nothing to care for.

It's soooooo nice just to relax and enjoy clear water with zero maintenance. I can see all my fish so clearly because of the bog.

 

[GBBUDD]

Some people feel there's only one way to build a bog and a pond. And that's simply not true. i used the basic gist of the bog and put my own twist on it . like poco said some have very deep bogs where they say it is detrimental as the oxygen is striped by the rocks and depth. I used the same principles as what is being brought into the latest's septic system designs along with the bog. i pump Oxygen / air into the bogs snorkel tube i do not pump it down the centipede i look at is as a draw pulling water from the other end of the centipede where the water is being pumped to so it's a push pull thing as i hope this will pull the debris to the snorkel for cleaning as the snorkel is a foot lower then the deepest part of the centipede creating a sediment trap. Water is influx with all the o2 can hold and feed the bacteria. I should clarify the o2 really doesn't feed the bacteria but it allows it the ability to run a marathon. We are all wearing these masks today and you know that if you try to run or do some exercise it's hard to do when the air is limited. so we can't work as hard .That s what I mean by feed the bacteria it allows it to have the necessary cardio to attack food deposits when they present them selves to the bacteria

 

[addy1]

poco said some have very deep bogs where they say it is detrimental as the oxygen is striped by the rocks and depth

They say the beneficial bacteria can't live that deep due to lack of oxygen. Meanwhile, many members here have way deeper bogs and they are doing great.

Mine is 2.5 plus feet deep, it does great! no added o2 nothing special just pea gravel and plants.