This is why I'm not a fan of "bogs".

[Mucky_Waters]

Before reading the rest of this post, please understand it is not my intent to offend anybody who either has or advocates "bogs", but rather to present my view on the mater and try and understand and hear from those who may use this system, their own understanding and experience with "bogs". Comment both pro and con are welcome. :razz:

To my understanding these bogs are, in essence, gravel or rock beds, that the pond water flows through. Correct me if I'm wrong?

The problem that I see with them is that over time they can, and will, collect organic sediment. Of course you really won't be able to see it because it will be covered by the rocks, but that doesn't mean that it's not there. So is there a problem with that? To my thinking, yes. That organic sediment inevitable begins to break down anaerobically, and when it does it produces hydrogen sufide (H2S) which of course is deadly toxic, not only to fish, but to humans as well.
Thing is, as long as that rotting organic mater is left undisturbed it will generally only release small quantities of H2S at a time, and fish (and humans) are able to tolerate low levels of this chemical. What I see as the problem is that over time more and more of this rotting organic mater will build up, and at some point it's going to be producing more H2S than the fish will be able to tolerate, then you will have a real, but unseen problem on your hands. I also would question why, if we are aware of this hidden problem, anybody would want to incorporate a "filter" system that has this potential for building and releasing any quantity of this deadly chemical into the environment with their fish (or other pond critters)?

Here is a short video of a sort of "bog", or "media bed" as it is referred to here, that is set up that is being used as a sort of hydroponic system for growing plants.
I will concede that this may be a more extreme case of this H2S producing organic sediment build up, but I think that any "bog" will eventually build up the same sort of organic sediment and also produce H2S.

 

[Mmathis]

YUCK! And I was just thinking "smell-o-vision" when he mentioned it in the video!

So, what would be suggestions for making a bog that could be easily & effectively cleaned? Would having "clean-out" pipes work? What about elevating the bog's floor by a few inches where the effluent would collect UNDER the gravel where it could be flushed out?

And why do some bogs WORK so well, yet some get a bad rep? There have to be things that factor into the equation......

 

[fishin4cars]

TM, I agree with Mucky, to a point. But at the same time, the results have been showing a different view for the most part. A canister filter or pressure filter can do the same thing, so it's something we have had to deal with for many years. In saltwater tanks it was thought that sand would do the same thing since it sits stagnant on the bottom of the tank with no water moving through it at all. Before reef tanks came along there were wet,dry filters which are similar in design to trickle showers in ponds now days. but as hobbyist tried it many found that the sand actually grew bacteria that helped in filtration in reef tanks and the trickle fitration was not as important as originally thought to be. In ponds I believe that something similar is going on. In a pond the plants and the bacteria are functioning as a natural filter, Does the muck build up under there, most certainly, and MUST be kept in consideration and maintained based on each individual set-up. A flush system I feel is a good idea, but also you must look at the whole picture and what will work best in your situation. I did two flush lines with the flow entering the center of the manifold. It has drawbacks, The flushing only works for the side opened so I have to do both ends in order to clear the pipes. Also, I just cleaned out part of my big, and yes there is some clogging going on, No rotten egg smell and when I clean what I did it really clouded the water but no effects to the fish, I did however choose to work through only 1/3rd of the gravel bed. My reasoning falls back to being a fish tank hobbyist. I don't like disturbing a complete filter system if it's not needed. I'll do a third, wait a week or two do another third, wait a week or so again and do the final third. This way I don't disturb all the bacteria and the stirred up area has some time to replenish Mucky brings up good points as well, and I too seriously debated the same things he is bringing up. I just haven't seen it happening. ( YET)? I am not closed minded to the possibilities that what Mucky is saying is true. I'll close this post with this. The pond with the bog has been consistent for the first year. 0 ammonia, 0 nitrite (past the new cycle) less than 10 ppm of nitrate all year, water has stayed crystal clear. and I even got spawning in the first year. and has NO UV light. Koi pond and no bog. ( I MUST NOTE: Both ponds have the same skimmer and filter falls units on both of them as secondary filters.) Has not stayed clear except for a few days at a time, is not as stable in water parameters but close, Has a UV light, and less stocking rate but by far is not responding as well as the pond with the bog. I'll have to wait and see what year two or year three bring. Again, I really don't know. But with running flow through bogs where the water flowed through floating plants I always had clear water. So I guess it's always a learning process to see if theory and actual results match or conflict.

 

[Mmathis]

Has anyone done actual water analysis to determine the amount of harmful chemicals that are in the water returning from a bog filter back into a healthy pond? And I mean from an undisturbed bog, not one where the settled muck has just been stirred. And to be scientifically fair, how does that water compare to water in a pond that wasn't filtered by a bog? Just curious -- not trying to start an argument, but trying to see it from both angles. I consider myself an advocate of bog filtration.

Seems like, if everything was in balance (whatever that means....), over time, even the "bad guy" muck & bugs would serve a purpose within the ecosystem of a bog filter.

 

[brandonsdad02]

I have 2 levels of filters in my skimmer box before anything reaches the bog. I have my leaf basket that collects the large stuff, then I have prefilters that collect some of the small stuff before it goes to the pump and then on to the bog and waterfall. I'm not sure on there set up but mine is loaded with plants, which eat most of that gunk. You can also get enzyms that will eat the sludge that is left which leaves even less to be cleaned. I have a friend of mine who has a raised floor bog. She has a empty void below her gravel that she cleans out every spring. She drains her 8,000 gallon pond every spring, sorts out her fish and sells some and power washes the whole pond and cleans out her bog pit.

 

[addy1]

No chemical analysis, just time and experience. Other pond (arizona) kept in good shape with my small bogs for about 10 years, never really cleaned them, did drain now and then maybe every few years, no horrendous amount of muck came out.

This pond, 4th year coming up, pond is always perfect in water tests, crystal clear, no algae issues. No stink when I dig up and pull out plants. No stink when it has been sitting all winter and I start the water flowing again. Just pea gravel dirt when I mess around in the bog, (I didn't wash my gravel) that cloud clears within a few hours out of the pond. I sometimes make it so cloudy you can not see anything.

I have leaf baskets before my pump to collect any large stuff. And a ton of plants in the bog. They get yanked now and then to keep them under control, but not very often, the frogs love to live in the bog. The birds bath in it, dragon flies lay eggs in it. Very neat bio system.

 

[SE18]

some good reading here! First year I cleaned out all the sludge (think worms that drown and die there, leaves and so on). It stunk pretty bad. Now, I'm just leaving it there as I don't have fish in my waterway and I'm thinking that frogs like to hibernate in the bottom sludge. I'm adding a lot of plants as well, thinking they have a good effect. I guess there are so many variables to consider and each bog is unique.

Our hounds lap up the water a lot. They probably have a good immune system!

I just don't want to create one of those killer lakes you hear about in Africa which bubbles up methane and kills all the neighboring villagers!

Dave

 

[CountryEscape]

I would like to know, Mucky, where your water is coming from before you find all that muck? Do you have soil in your gravel pits with plants? I cannot imagine what is creating all that muck in such a short time? The only dirt that got put in my plant bog was from potted plants, which I was quickly reminded was not necessary. If it's a tropical plant, I pull the pot and all. There is no muck in my bog either. I've pushed hand down into the gravel to pull and plant, and as Addy said, just silt from the original gravel. When I disturb the bog a lot, I simply drop the outer edge, let any foggy water drain out onto the grass. The muck and sludge we ponders with fish can expect would have to do with fish waste, which is becoming fertilizer for the plants. Not sure again where your muck is coming from, as I only saw trenches of water and the trench with plants looked very much like it had either soil or mulch or both included with the gravel. Obviously, if there is soil and mulch, that is going to break down, thus becoming muck. Please explain further, as I'm certain that is not the case, but I have a very hard time understanding where you are coming up with all that muck in 3 months with simply pea gravel and bare rooted plants! Do you have a pond that the water is filtering from that was not shown in the video perhaps? Thanks for your great video. I tend to agree with Larkin. My only difference is that my large bog (1/3 or more of pond surface is bog area) is in the goldfish pond, which has approximately 25 goldfish from 2" to 8" in length, and my much smaller bog is on the koi pond. The koi pond is NEVER as crystal clear as the goldfish pond. Both ponds have excellent water quality as well. I have the ability to flush the pipes, mainly to get rid of anything that may be clogging the 1/4" holes that the water flows through.
I look forward to more information on your part, Mucky, as to where the water originates from that becomes your muck. :razz:

 

[fishin4cars]

TM, that kind of testing would be so costly. I doubt any hobbyist has that kind of equipment to do the kind of testing that would be required to get accurate tests. But it would be interesting to know if someone could. CE, Mucky doesn't run a bog, his post is based on what "COULD happen, and it's very real. It's something that should be looked at in design and maintenance. The so called muck is going to get in there even if it's just from the water column. Pre-filtering can help slow down the process of how much build up occurs but at the same time it could be depriving the plants of the nutrients too, It's a balance as with any other type of filtration. On Mucky's pond there is virtually no chance of this happening due to his design in his pond, there are only a very few places in his pond where a build up could even take place and even then the areas that could are so small that they can be managed very easily. In ponds that have rock bottoms this is a very common problem, the reason is that the muck builds up where there is little or no water movement. The oxygen is depleted and the (Quote from Mucky's Post) quote frome muckyorganic sediment inevitable begins to break down anaerobically, and when it does it produces hydrogen sufide (H2S) which of course is deadly toxic, not only to fish, but to humans as well. IMO, if the bog is not allowed to clog and channel there is a lot lower chance that this will take place as the water is constantly moving through the gravel bed, Now if the bog is not cleaned and water starts channeling through it, then the case in point could very easily take place. Another scenario that I have thought about and worries me is those hobbyist that have bogs and have to shut them down for winter. When these bogs are started back up in the spring they could EASILY have this nightmare come back to haunt them. My suggestion would be to flush and stir and get as much water flushed through the system when starting back up in the spring as possible if it has been shut down for any length of time. Lucky for me that hasn't been the case. I have been able to run year round and have not seen then effects so far to date. Not saying that aren't happening or haven't and not saying they won't either.

 

[Mucky_Waters]

Thanks for all the responses.

First let me say, that video is not mine, I just came across it while following up some links I saw in another forum, and as I mentioned from the start, I admit that it is probably an extreme case. I simply found it to be a very good example of what I feel to be the main negative attribute of using a bog as a filter system for a pond or water garden. I'm sure they work as well or maybe even better than other filter systems, but they generally lack one key quality that most of us wouldn't accept in any other type of filter design, and that is the ability to easily clean them out on a regular basis. Lets face it, any pond filter is going to collect sludge. The make up of that sludge is usually made up of more than just fish waste, dead plant mater, blown in dirt and debris, dead fish and insects (earthworms) are a large part of that sludge as well. It all ends up somewhere.
In my pond I have a settling tank with a cone shape bottom and drain valve. I generally don't get a lot of junk down there, but every once in a while I'll open the drain valve and drain off about a half a gallon of the sludge from the bottom into a container, and boy does that stuff stink! The top exit flow pipe of that settling tank has a screen that catches the lighter stuff that doesn't sink to the bottom of the settling tank, and I actually get more gunk accumulating in that top screen than settles at the bottom, but the stuff in the top screen never develops that rotten egg smell because it always has fresh (oxygenated) water flowing past it and never goes anaerobic like the stuff that settles to the bottom does. The problem I see with bog filters is they act like big settling tanks, but they have no way of draining that anaerobic sludge out of the bottom. That compounded with the fact that in most designs people really have no way of knowing just how much junk is accumulating down there. In the video the guy has that bottomless metal drum that extends to the bottom of his rock media bed. I think that would be a good idea for people who do set up in their bog to give them access to the bottom of their rock bed so they could monitor how much sludge accumulation they really have going on down there.
Larkin mentions building some sort of system for flushing out the bottoms of the bogs, I would have mixed feeling about that. There is no question that you will get anaerobic sludge buildup at the bottom of a bog, the one thing that stops it from contaminating the rest of your pond is that if it is left alone the H2S stays mostly in the sludge and is only released into the water flow in very small quantities. If you were to allow it to accumulate for a long time and did a rapid flush there would be a sudden release of the H2S that could be lethal to your fish. It would be very hard to predict how often you could, or should, flush a system without causing harm.
Addy mentions that she had a 10 year old bog system that she "never really cleaned". It would have been interesting had she dug it up to see just how much accumulation she really had down there after 10 years, she might have been shocked.

Larkin also mentions that you can get sludge build up in other types of filters, and that's true, but every other filter system is designed to be cleaned out periodically, and cleaned out in a way that the water you clean it out with doesn't get flushed back into the pond with the fish. To me, bogs are sort of like huge sand filters, only worse because they accumulate sludge that can go anaerobic, because the constant water flow in a sand filter gunk build up doesn't normally get a chance to go anaerobic. Also when you back flush a sand filter you would never back flush the effluent water from a sand filter into your pond water, and you would never build a sand filter without a proper way of back flushing it to clean it out.

Brandon'sdad mentions his friend who has an empty void under her gravel bed that she drains out every spring. Perhaps something like that coupled with a good flushing might be a working solution, providing when you flush it you are able to flush it really well, and you don't flush it into the pond water.
In summary, I don't have a bog, but I think they probably work as a pond filtering system, and possibly work quite well, it's just very obvious that over time a bog WILL accumulate sludge, that sludge WILL go anaerobic. That anaerobic sludge WILL produce H2S. H2S IS very toxic. The only question is, if you have a bog how will (do you) you deal with it? Or do you deal with it?

Again, thanks for your replies.

Edit: looks like me and Larkin were posting at the same time.

 

[fishin4cars]

Mucky, One thing I think you may have overlooked is that I know Addy, Todd, myself, and CE all have set up back flush valves that don't dump the water back into the pond, they dump out the back or sides and into flower beds. BTW, plants do seem to really love this stuff! The problem I'm seeing is even when back flushing it really never removes the build up in the gravel, it more clears the holes/slits cut in the pipe for better flow rate and only a small amount of the debris that are caught are removed back out of the system. One of the key factors I believe is going on is in a bog where there is a good flow rate is the bacteria are given some oxygen. In a sump area, or in the cone of the vortex the lower the level and the more still the water the more oxygen that is deprived from the bacteria. This tends to be where smell comes from most often, In bogs these same areas seem to attract more plant roots, so possibly there is a coloration between this area/ the chemical exchange/ the bacteria/ and the plant roots that is beneficial? similar to what is found in a reef tank.

 

[CountryEscape]

Wow, this thread has had some really good ideas, thoughts, explanations, and considerations for bogs. I thank Mucky for starting it, and everyone else for chiming in. This spring, when I thin out my plants in the bigger bog (which will only be 1 year old), I will do some stirring up on purpose, just to see what is accumulating down deep in the gravel. Obviously, since my gravel is 12-16" deep, I won't stir it up that deep, but I will get an idea if sludge is beginning to accumulate. And, as I said, I will not allow any of this mixed up dirty water to flow into the pond, but will rather lower the side on the outside of the bog and let it flow into the grass behind it.
Anything we can do and learn to better take care of our fish, frogs, plants and environment is worth reading. I'm always up for more learning, since I consider myself still a beginner.

 

[Mucky_Waters]

Mucky, One thing I think you may have overlooked is that I know Addy, Todd, myself, and CE all have set up back flush valves that don't dump the water back into the pond, they dump out the back or sides and into flower beds. BTW, plants do seem to really love this stuff! The problem I'm seeing is even when back flushing it really never removes the build up in the gravel, it more clears the holes/slits cut in the pipe for better flow rate and only a small amount of the debris that are caught are removed back out of the system. One of the key factors I believe is going on is in a bog where there is a good flow rate is the bacteria are given some oxygen. In a sump area, or in the cone of the vortex the lower the level and the more still the water the more oxygen that is deprived from the bacteria. This tends to be where smell comes from most often, In bogs these same areas seem to attract more plant roots, so possibly there is a coloration between this area/ the chemical exchange/ the bacteria/ and the plant roots that is beneficial? similar to what is found in a reef tank.

Thanks Larkin, I did read your flush method in your first post and no doubt it helps a lot. This is why I'am asking these questions. Do you have any pictures or diagrams of your bog plumbing?

I agree that with proper water flow any debris or sludge isn't likely to become anaerobic, but I know from my settling tank, which has a great deal of flow by the way (too much really), that it doesn't have to be far out of the flow to start getting anaerobic. I believe that the only part that really gets anaerobic in the settling tank is the sludge that has worked it's way down the drain tube, which is a 1 1/4" pipe that is less than a foot long. I could remove that anaerobic portion just by draining a cup of water, but I usually release a little more (1/2 gal) to try and drain the rest of the muck in the bottom of the tank. Yet that small 1 cup of anaerobic sludge is some pretty foul and potent stuff.
I guess a lot depends on how efficiently your bog system is set up to flow. I would think a bog would benefit from some 6" or 8" access pipes that would allow you to open a cap and either, visually inspect, or use your hand to manually inspect the bottom of your bog for accumulated sludge.
You mention aquariums a couple times, and when comparing bogs and sand filters I'm also reminded of the under gravel filters that aquariums often use. I guess a bog could sort of be similar to an up flow under gravel filter, which was preferable to a down flow under gravel filter which tended to trap debris and clog more easily. Those things had a hollow false bottom that the gravel sat on and, in the up flow systems, the water flowed evenly up through the gravel, which maybe very comparable to how Brandonsdad's friend's bog works, with her "hollow bottom".
As for plants in bogs, I refer to the video I posted at the start of this thread. That guy had a lot of plants in his system, judging by the amount of sludge he was draining out of his bogs I don't think they were helping all that much.

 

[Mucky_Waters]

This spring, when I thin out my plants in the bigger bog (which will only be 1 year old), I will do some stirring up on purpose, just to see what if accumulating down deep in the gravel.

Please CE, post your findings here. Pictures and video make it even more interesting. Always eager to learn and see how other people manage their ponds.

 

[CountryEscape]

I had my pics handy, since it's been less than a year. I think these will give you an idea of how the water goes in and flows through the gravel.
Drilled 1/4" holes in the pipes that would lay on the bottom of the bog (placed the holes facing down, so the water had to work harder to find it's way up through the gravel, to the overflow back into the bog.

Here is a pic of the plumbing parts where they split from the line coming from pump to feed the bog.

Then the pipes laid out the length of the bog. I just made one bend in the line, others may have made it "prettier" and had more of a curve, like the actual shape of my bog.

Here are the clean out ends. Just capped the ends, not glued. Only have had one pop off so far, so put a rock on top. The tops are just above the surface of the pea gravel, but I have an elbow and long pipe that attaches to it when I flush it.

Then came the gravel, and water. I lowered the outside edge of the bog to drain out most of the silted up water before I let the water start running into the pond. I have two wells, so used them to flush and clean the gravel, which worked really well, since I could drain the water out of the bog, and not into the pond.
Hope these help!
I will post pics this spring, Mucky. I hope these pics help to see what is under all that gravel. I just know that the goldfish pond has been crystal clear since the get go, never did turn murky like the koi pond did this spring (2nd year for koi pond, so maybe this year the goldfish will have that problem, we shall see). Right now, I can go outside and take pics of all of the fish not hiding under the ice. Water is very clear. Bog was running until this past week, electricity blew breaker while I was at work, and I want to wait until I know the water lines are clear of ice before turning pumps back on.