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

[crsublette]

Howdy Mucky!!

Paul is an interesting fella. I have really enjoyed watching his videos and reading his articles. He is being quite an innovator and teacher in this arena of proper bed making for plants utilizing wicking in an aquaponic system for his specially designed Earthan aquaponic system. I am glad Paul did this demonstration video to help explain the effects of a typical bog. For anyone interested in Paul's work, checkout http://www.earthangroup.com.au.

Ultimately, any filter will become anaerobic if not properly designed nor properly maintained.

Also, I think it is quite an exaggeration to suggest Paul is incorrect due to the fact that "your", nor you, have experienced any issues thus indicating there are absolutely no problems with it at all, which is quite absurd.

Bogs are exactly just a sand & gravel (S&G) filter with plants on the top. S&G filters are basicly just water polishing, fine particulate filters. All organic materials will break down into mulm, also called detritus. Mulm is not a sterile product. With agitation of this mulm and further decomposition, this creates the dissolved organic particulates (DOP). A benefit of plant roots is they excrete aglutinins which act as a focculant, that is allowing the DOP to better settle in water. Essentially, plants allow your pond resevoir to become a better settlement chamber, which is good. However, it is enivitable that this mulm will get trapped in the gravel until the mulm is decomposed further into DOP so to be settled on the floor of the pond or drained through a pipe at the bottom of the bog. Every single pond video, with bogs, I have seen has a noticeable layer of mulm near the surface of the bog or at the floor of the pond. Plant roots also excrete a low volume of oxygen so there will be a general area around plant roots that will deter anaerobes from producing the H2S.

To obtain the exact same processing cabilities of Bogs, a single 55gal S&G filter plus an effecient bio-filter and simply just puting the plants in the pond. Also, this is tremendously easier and more energy efficient to flush a S&G filter, and, if the water is properly filtered, then the bio-filter would rarely ever needed, or at least twice a season, to be flushed.

An even better bog is one where the water is pre-filtered very good prior to entering the bog and is allowed to be purged on occasion. I doubt any harm would come to your fish if all ya do is disturb the area around the plant's roots, such as when pulling them out or are only planting in a 6" depth or so. Also, if there was any H2S released, then this oily substance would likely become obstructed on the bog's surface, diluted quite a bit, prior to entering the pond.


Bogs are fine, but lets not kid our self about what is happening, which is a role of nature.

 

[crsublette]

For anyone interested in Paul's work, checkout http://www.earthangroup.com.au.

For anyone curious, Paul is also active on the APHQ forum as well.

 

[Paul Van der Werf]

Hi guys,

Is there anything you need clarified about this set up. I can appreciate not many wetlands,bogs,growbeds will suffer this heavily. The video was to example even with extensive, passive filtration, the growbeds microbial mass generates substantial wastes which if not managed will (in time) present a health issue for both your plants and fish. In a lower density fish situation, you will have a much longer time before this happens.

Regards
Paul

 

[Mucky_Waters]

Hi Paul
Thanks for dropping in.
I thought your video was very informative, which is why I linked it here. It demonstrates well what sort of nasty stuff can build up, unseen, in a bog. I thank you for posting it on youtube.

I have a couple questions for you now that I have you here.
With regards to that "nasty stuff", you say " In a lower density fish situation, you will have a much longer time before this happens.", but do you think that it is so bad because of the heavy fish load, or do you think it might be more from the soil you used in your grow beds?
Also, have you had any health problems with your fish possibly related to the release of H2S from that contaminated water?

Thanks
Mucky

 

[Mmathis]

Hi, Paul! See my post #2 at the start of this thread. I'm in the process of building a bog filter (planning stages) for my garden/goldfish pond, and am open to suggestions on ways to make it operate more efficiently while avoiding the excessive waste buildup. What (and how) steps can the average pond owner take to minimize "toxic" outcomes? Is the answer in the construction, maintenance, both, or something else?

 

[Waterbug]

Be careful of over reacting. Hydrogen sulfide is almost never a cause of fish loss in ponds. Yes it's toxic...at certain levels. So is CO2, ammonia, nitrite, etc all of which are primary killers. It is difficult for hydrogen sulfide to build to toxic levels in most backyard ponds because water movement out gases it very well, just as CO2 is out gassed. Couple that with how slowly hydrogen sulfide is produced and it's threat is very low.

Hydrogen sulfide is produced in our own guts and inside fish too. Ground water can be a primary source.

However, in high fish load ponds anything that reduces O2 is considered a danger. In these kinds of ponds even low levels of hydrogen sulfide would be considered a serious problem because if you have hydrogen sulfide you'd also have high CO2 and low O2 because of low water turn over and a lack of gas exchange. In these kinds of ponds no organic decomposition can be tolerated because it would consume O2. Keepers of these kind of ponds would never ever consider a bog to be a viable filter. But their main issue would be O2 use primarily and then probably bacteria, hydrogen sulfide is pretty far down the list.

Most of the harm in decaying organic matter happens in the first few days. When you disturb muck you definitively can smell strong hydrogen sulfide...because it was trapped, which allowed it to accumulate over a very long period. Key word is "trapped". Trapped hydrogen sulfide does not enter the water, it's trapped. When disturbed and released 99.9% of it goes directly into the air, which is why you smell it. The biggest source of hydrogen sulfide into the water column is going to be a very thin layer of waste, what most people would considered a "clean" pond. Even thin layers can be anaerobic, and it's thin layers where the produced hydrogen sulfide can actually make it into the water.

One of the few cases where I read hydrogen sulfide may have been the cause of a fish die off was in what most people would consider a clean pond where the fish were being fed a lot of high quality food (worms I think). The fish were young, high fish load and were being heavily feed in order to produce max growth (it was a contest). Some food wasn't being eaten and one day all the fish were found dead. No way to know if hydrogen sulfide was the cause, but it was suspected and I think it was a reasonable guess. The accumulation of waste was a pretty short period, days, maybe a couple of weeks.

I've never seen any research or even reasonable theories that show a build up of muck to be a danger to fish --- assuming reasonable fish loads. When you get into higher fish loads it's really more the fish load being the main issue and in those conditions, yeah muck would never be tolerated. Long, long before muck could build up waste has to be removed in those kinds of ponds.

It's also absolutely true that any filter that traps waste and keeps it in the water column is going to have the same effect as a bog. That's why I'm not big on submerged media filters, they're the worst of both worlds. At least a bog is a good settling tank, it has some use.

The measurement of this issue is normally done with an ORP meter. This doesn't measure hydrogen sulfide directly but instead stuff that would be associated. If water has a high organic content you can assume other things like high CO2, HS, and lower O2. Because hydrogen sulfide out gasses so well it is not that ease to measure.

IMO bogs, or any submerged media - settlement type filter or neither good or bad. They simply are what they are. It depends on the kind of pond and what kind of pond a keeper wants. The higher the fish load the worst these filters are. But for most backyard ponds they're perfectly fine and can even improve water over what the pond would be without any cleaning at all.

As far as cleaning a bog, or keeping it clean, I don't see where that would be reasonable. Yes you can add a drain system and when you open it dirty water will come up and if that makes someone happy then cool. But as far as that improving water quality...I'd never buy that. IMO disturbing the waste only releases trapped toxins so to me that would be a bigger threat.

And on the subject of toxins...hydrogen sulfide is the one web sites like to dwell on...we can smell it, it smells bad so it must be bad. But there are many more kinds of toxins, like heavy metals, that are released from decaying organic matter. Lot's of decaying organic matter means these build up. They also remain in the muck unless disturbed. But if anyone like hand wringing there are scarier things than hydrogen sulfide.

Bottom line is the cleaner a pond the better it is for fish. Just a question of how much effort you want to invest. But that doesn't mean some level of fish load can't survive in a less than spotless pond.

 

[crsublette]

WB, your first hyperlink gives a page error, no data shown. It appears their database is a little screwy. What's the title of the document you are referencing ??


I have definitely read testimonies of fish kills in low fish density ponds with rock bottom ponds while the person dramatically lowered the water in the pond and was cleaning the pond with the fish in there. The person killed all of their fish, but I don't know if it were due to the sudden release of big pockets of hydrogen sulfide or if it were the bad bacteria on the particulates that entered the fish's gills.

As mineralization progresses, muck is created, which contains all sorts of inorganic properties and is not inert to anaerobes. Muck is full of carbons and organic nutrients constantly diffuse into it, always housing bacteria, that continually feeds bacteria, further decomposing the muck, so it is always using oxygen.

From what I've read, poor water circulation and accumulation of organics are both required, not fish density, is what depletes oxygen. Sure, a higher fish density can traumatically speed up the DO consumption.

From what I understand, it takes an incredibly low oxygen saturation, somehwere below .5mg/L, for anaerobes to produce hydrogen sulfide; otherwise, the anaerobes reduce the organics into ammonia or produce nitrogen (N2) gas that gets gassed off. So, the water's DO levels would have to be noticeably depeleted for a thin layer of anaerobes to produce any hydrogen sulfide (H2S). There are various population levels of anaerobes throughout all layers of the muck and water, as described in the analysys of a mud pond in China, physico-chemical factors and bacteria in fish ponds. From what I understand, it is the concentration of the water's DO that causes the problem and the fish will generally be staying out of the areas where the DO drops below 2mg/L unless the DO in the entire tank dropped significantly.

As far as I am aware, for bogs or gravel filters where water is forced up into it, only way to provide good aeration is through a purge aeration process.

I suppose the more correct question would be... How much compaction and how many layers of muck does it take to suffucate, or reduce, the DO saturation to the anaerobes?

 

[crsublette]

Also, I am pretty sure Paul's video recommends to not dump the drained, purged, or dislodged waste back into the fish tank.


The major difference between Paul's Earthan beds and bogs is how the water is delivered to the plants.

For bogs, water is forced up through the material. This force of water increases compaction. As the water is forced up, this forces all sorts of dissolved organic particulates up into the gravel as well.

For the Earthan beds, the water is wicked, not forced, up to the plants; Wicking Bed technology is a good reference describing the wicking process. The plant medium used determines how far water wicks up through the medium. For the earthan beds to work well, a soil mix must be used that is loose and does not easily become compacted.

Wicking is really quite interesting. In farming and when the farmers can afford the installation, there are huge fields that using underground drip irrigation and this irrigation is buried about 12~14" in the soil. The irrigation is operated like your lawn irrigation where there are many stations in a field and, when station1 turns off, then station2 turns on. The drip emiters are extremely low rated so water is not forced into the soil at all; the absorption properties of the soil pulls the water up to the top. As the water is slowly pulled by the soil toward the surface, the water is also aerating the soil and this provides just enough oxygen to prevent the production of the ill effects involved with soil too moist. When the station is turned off, the soil remains noticably fluffy, After wheel tracks are made on top the of the ground and as the drip irrigation cycles, you will actually see where the drip line is buried since the soil is actually lifted up a bit higher in those spots; it's quite an interesting to see. The soil become incredibly soft, not compacted at all.


Mmathis, I think Paul might recommend building your bog where water is not forced up through it and, instead, the bog is on top of a deep water resevoir where the water wicks toward the plants; this will remove the "fines filtration" feature of the upflow bog. So, on his website, Paul also highly recommends seperating solids, through a mechanical filter or settling tank, prior to the water entering the resevoir below the gravel. In the video, you will notice the deep water culture beds act as a settling tank. I'm not for sure what the proper depth of the gravel should be so that the wicked moisture actually can reach the plants.


Hopefully, when Paul returns, he can elaborate further on Mucky's and Mmathis' questions.

I have a question as well. Paul, as ya stated, "growbeds microbial mass generates substantial wastes which if not managed will (in time) present a health issue". How would you properly manage this microbial mass's waste accumulation in a bog or in your Earthan beds ??

 

[Mucky_Waters]

I don't see anybody over reacting or wringing their hands here, just a group of people discussing bogs and media beds. Nice try though.


Although most of what Waterbug says makes sense, one thing to consider is that according to the Environmental Protection Agency, a maximum acceptable level of H2S for fish and aquatic life is around 0.002 ppm. The threshold for detectable smell in water starts around 0.05 ppm, so what that means is, if you can smell that rotten egg smell in your pond water (without manually stirring anything up), then your fish are probably already in distress.

Apart from any H2S issue, I guess my biggest issue with bogs is that unlike other pond filters, which can also accumulate muck, bogs are not (normally) designed to be cleaned out or inspected like other filters. Charles accurately compared bogs to rock bottom ponds, I think that is a good comparison, left unchecked they can quietly and covertly just keep accumulating muck until basically the only thing you can do is remove your fish (and other critters if you have them), shut the pond down and do a complete overhaul by digging up all that rock and muck. It just seems like an unnecessarily large chore that could otherwise be avoidable by using some other type of filter system, or perhaps a better bog design.
Show me a bog design that can be thoroughly flushed out and easily inspected, without shutting the pond down and digging up all the rocks, then I'll become a fan.

 

[Paul Van der Werf]

Thanks for the welcome.

I will endeavor, as time permits, to tackle some of the questions and concerns raised one at a time.

1. With regards to that "nasty stuff", you say " In a lower density fish situation, you will have a much longer time before this happens.", but do you think that it is so bad because of the heavy fish load, or do you think it might be more from the soil you used in your grow beds?
2. Also, have you had any health problems with your fish possibly related to the release of H2S from that contaminated water?

1. The vid, shows a gravel filled grow bed, there is no soil in that particular set up. The wicking bed next to it (where I am pumping oooze on my hands in the vid), runs on overflow and backwashing of the filtration so the water entering that bed is a one way trip. We have built a few large aquaponc set ups using soil as the growing media but the water does not often come in contact with the soil and the water is constantly running. The key to making them work properly and avoiding this nasty issue is oxygen. The Earthan Beds have passive aeration before and after the water enters the bed. It is definately a result of heavier fish loads or more to the point feed loading.
2. No, none ever, even in the set up in the video. The vid was more of a response to "gurus" suggesting that media filled grow beds did not need prefiltration at all and the beds have the capacity to mineralise all fish wastes. While that might be true for 5kg of fish per 1000 litres, it is not for higher densities. Even this system has 25kg/m3, with substantial filtration (ecluding micron) and the beds themselves generate a huge amount of inorganic sludge which in time would require cleaning. The "gurus" are misleading was the point I suppose.

Regards
Paul

 

[crsublette]

Thanks Paul. I look forward to read more!

Show me a bog design that can be thoroughly flushed out and easily inspected, without shutting the pond down and digging up all the rocks, then I'll become a fan.

Hmmm... (bah, I miss using koiphen's emoticons)... I suppose you could design the typical upflow bog like a s&g filter where ya insert sections of tubes, each suction has its own blower, then turn all the blowers on at once... then, build something so you can temporarily divert the dislodged waste away from the pond (i.e., fish tank). Then, turn off the blowers and continue to divert the water until it clears up. Sheesh... this would be quite a bit of blower power... I wonder what the boil would look like.

 

[Paul Van der Werf]

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.

Hi Mucky,

The H2S is not quite that much of a problem unless you are in an enclosed environment.

The point of primary failure is when the beds (or bogs - where I come from a bog is something entirely different and plenty of methane is assocated), become overloaded with organic solids from too much input and not enough mineralisation of the organics by heterotrophs (and others microbes fungus and what nots). This can be temperature, hydraulic loading and a range of chemical issues but primarily it is organic solids loading.

A few things happen quite quickly, the bed becomes anaerobic which has been discussed and the hydrogen sulfide and methane produced as a by product waste from bacteria chewing down on the organics.

Once those heteros take over, their population explodes very quickly and outcompete your nitrifiers that keep the ammonia and nitrite nitrogen levels in check, for space on substrate, food and oxygen. I have seen very large biofilters collapse as a result and kill tonnes of fish.

The other side to that equation, as many of you will know is once the bed becomes anaerobic, the heteros start to look for other sources of oxygen goodness and so they start on the nitrate nitrogen (NO3), reducing it back to nitrite by sucking up some oxygen (NO2) and at times they stick there for some time elevating your nitrite nitrogen to levels beyond your capacity for the fish chloride pump to cope with.... then the heteros take up the last bit of oxygen and the nitrogen gases off to atmosphere as N2 (no Oxygen left in it). While denitrifying is handy to reduce water exchange majority of the time in unmanaged systems, the nitrite spike is consistant and deadly to the fishes.

The second issue is when the beds (bogs) are full they begin to discharge a sneekier (is that a word?) problem. The start to resuspend the fine solids into the water column and ultimately into your fish habitat. Levels above 20mg/L of total suspended solids (really fine stuff) will irritate gills and reduce oxygen diffusion, with the end result of disease, reduced growth and in most cases death. But a very sneeky death, because there are not many obvious signs of what happened.

In short, I don't think the H2S is such an issue provide you have good aeration in your pond where it will quickly gas off.

Regards
Paul

 

[Paul Van der Werf]

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.

Not so much the harful chemicals but we will be doing some more later. This is what we have so far, just a comparison with worm tea...in the system in the vid.
http://www.earthangr...quaponic-water/

Regarding the "if everything was in balance" I am not convinced that is such an easy thing to do in a dynamic environment like media beds (bogs).

Regards
Paul

 

[crsublette]

If I can, got another question to add on to the list.

The second issue is when the beds (bogs) are full they begin to discharge a sneekier (is that a word?) problem. The start to resuspend the fine solids into the water column and ultimately into your fish habitat. Levels above 20mg/L of total suspended solids (really fine stuff) will irritate gills and reduce oxygen diffusion, with the end result of disease, reduced growth and in most cases death. But a very sneeky death, because there are not many obvious signs of what happened.

When stated "levels above 20mg/L of total suspend solids", I am not familiar with the EC test or TDS tests expressed in mg/L. Can the "total suspended solids" be found as a result of an equation with data provided by EC test or TDS test values or is it the result of a completely different test that I might be able to conduct ??

Unrelated question.... When there is heavy rains or apply a fertilizer drench on top of your Earthan beds, can this cause a compaction problem in the soil mix ??

 

[crsublette]

To be more precise, when I wrote "fertilizer drench", I am referring to the various compost and worm tea mixtures.

Unrelated question.... When there is heavy rains or apply a fertilizer drench on top of your Earthan beds, can this cause a compaction problem in the soil mix ??