Plenum system in live sand? anyone tried this?
- Thread starter camp6
- Start date
Most people do not use plenums, but instead just use a deep sand bed. Current thinking is that the DSB offers the same or similar benefits of a plenum, but without the difficulty in set-up and with less risk of disruption.
There are certainly lots of people who do use plenums with success, but I think the majority of folks here just use DSB with similar success. If you do searches here on "Jaubert," "plenum," "DSB" and "deep sand bed," you should get a ton of information about how to set each system up properly.
ReefLion
There are certainly lots of people who do use plenums with success, but I think the majority of folks here just use DSB with similar success. If you do searches here on "Jaubert," "plenum," "DSB" and "deep sand bed," you should get a ton of information about how to set each system up properly.
ReefLion
I totally disagree. The benefits of a plenum system, if properly constructed, far outweigh the DSB concept. Here's why:
The plenum offers an anarobic region (oxidation) and an anoxic region (reduction) It is the only architecture that can bring about he total process of nitrogen metabolic process from ammonia to nitrogen gas. In the DSB, it is really guess work on how deep, what grain size, and surface flow rate that will bring about partial nitrogenous processing. The anoxic regoin in the plenum is where the reduction of nitrate to N2 gas occurs.
Do dont be mistaken, the "flow" of nitrogenous compounds through a DSB or plenum does not occur due to imparting energy to water (flow rate), rather, from ionic attraction. Negative attracts positive, and negative repels negative.
The ammonia molecule is attracted by charge to the anarobic regoin (top layer of the plenum, there it is oxidized into nitrite, then nitrate. The nitrate molecule is further attracted into the reductive layer (anoxic later= low O2) close to the plenum grid, where it is reduced to N2 gas and diffused back into the water column, where it is off-gased at the aquarium surface to the atmosphere.
The anoxic regoin of a plenum is up to a centimeter thick. In a DSB, it is about the thickness of a sheet of paper. The sand in a DSB below this anoxic regoin is a nutrient sump, where anarobic (oxygen free) microbes will produce hydrogen sulfide -which of course, is bad.
I recommend you order the pamphlet on deep sand beds and plenums called: "Live Sand Secrets" -A dialogue on living sand filtration, by Bob Goemens, Ph.D. You can find it on Amazon or about 6-7 bucks. It's quite enlightening, and contradicts the last post in spades.
The only way to improve upon a plenum system is to make it ap plenum/refugium.
:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:
The plenum offers an anarobic region (oxidation) and an anoxic region (reduction) It is the only architecture that can bring about he total process of nitrogen metabolic process from ammonia to nitrogen gas. In the DSB, it is really guess work on how deep, what grain size, and surface flow rate that will bring about partial nitrogenous processing. The anoxic regoin in the plenum is where the reduction of nitrate to N2 gas occurs.
Do dont be mistaken, the "flow" of nitrogenous compounds through a DSB or plenum does not occur due to imparting energy to water (flow rate), rather, from ionic attraction. Negative attracts positive, and negative repels negative.
The ammonia molecule is attracted by charge to the anarobic regoin (top layer of the plenum, there it is oxidized into nitrite, then nitrate. The nitrate molecule is further attracted into the reductive layer (anoxic later= low O2) close to the plenum grid, where it is reduced to N2 gas and diffused back into the water column, where it is off-gased at the aquarium surface to the atmosphere.
The anoxic regoin of a plenum is up to a centimeter thick. In a DSB, it is about the thickness of a sheet of paper. The sand in a DSB below this anoxic regoin is a nutrient sump, where anarobic (oxygen free) microbes will produce hydrogen sulfide -which of course, is bad.
I recommend you order the pamphlet on deep sand beds and plenums called: "Live Sand Secrets" -A dialogue on living sand filtration, by Bob Goemens, Ph.D. You can find it on Amazon or about 6-7 bucks. It's quite enlightening, and contradicts the last post in spades.
The only way to improve upon a plenum system is to make it ap plenum/refugium.
:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:
I totally disagree. The benefits of a plenum system, if properly constructed, far outweigh the DSB concept. Here's why:
The plenum offers an anarobic region (oxidation) and an anoxic region (reduction) It is the only architecture that can bring about he total process of nitrogen metabolic process from ammonia to nitrogen gas. In the DSB, it is really guess work on how deep, what grain size, and surface flow rate that will bring about partial nitrogenous processing. The anoxic regoin in the plenum is where the reduction of nitrate to N2 gas occurs.
Do dont be mistaken, the "flow" of nitrogenous compounds through a DSB or plenum does not occur due to imparting energy to water (flow rate), rather, from ionic attraction. Negative attracts positive, and negative repels negative.
The ammonia molecule is attracted by charge to the anarobic regoin (top layer of the plenum, there it is oxidized into nitrite, then nitrate. The nitrate molecule is further attracted into the reductive layer (anoxic later= low O2) close to the plenum grid, where it is reduced to N2 gas and diffused back into the water column, where it is off-gased at the aquarium surface to the atmosphere.
The anoxic regoin of a plenum is up to a centimeter thick. In a DSB, it is about the thickness of a sheet of paper. The sand in a DSB below this anoxic regoin is a nutrient sump, where anarobic (oxygen free) microbes will produce hydrogen sulfide -which of course, is bad.
I recommend you order the pamphlet on deep sand beds and plenums called: "Live Sand Secrets" -A dialogue on living sand filtration, by Bob Goemens, Ph.D. You can find it on Amazon or about 6-7 bucks. It's quite enlightening, and contradicts the last post in spades.
The only way to improve upon a plenum system is to make it ap plenum/refugium.
:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:
The plenum offers an anarobic region (oxidation) and an anoxic region (reduction) It is the only architecture that can bring about he total process of nitrogen metabolic process from ammonia to nitrogen gas. In the DSB, it is really guess work on how deep, what grain size, and surface flow rate that will bring about partial nitrogenous processing. The anoxic regoin in the plenum is where the reduction of nitrate to N2 gas occurs.
Do dont be mistaken, the "flow" of nitrogenous compounds through a DSB or plenum does not occur due to imparting energy to water (flow rate), rather, from ionic attraction. Negative attracts positive, and negative repels negative.
The ammonia molecule is attracted by charge to the anarobic regoin (top layer of the plenum, there it is oxidized into nitrite, then nitrate. The nitrate molecule is further attracted into the reductive layer (anoxic later= low O2) close to the plenum grid, where it is reduced to N2 gas and diffused back into the water column, where it is off-gased at the aquarium surface to the atmosphere.
The anoxic regoin of a plenum is up to a centimeter thick. In a DSB, it is about the thickness of a sheet of paper. The sand in a DSB below this anoxic regoin is a nutrient sump, where anarobic (oxygen free) microbes will produce hydrogen sulfide -which of course, is bad.
I recommend you order the pamphlet on deep sand beds and plenums called: "Live Sand Secrets" -A dialogue on living sand filtration, by Bob Goemens, Ph.D. You can find it on Amazon or about 6-7 bucks. It's quite enlightening, and contradicts the last post in spades.
The only way to improve upon a plenum system is to make it ap plenum/refugium.
:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:
Apparently some users of plenums also vehemently support their techniques to the exclusion of others. I'm not sure why, given the success many people have had with deep sand beds.
I suggest you read the book mentioned by the previous poster, and read everything else you can get your hands on, including the many posts on this board on both topics, and then make your own informed decision. Regardless of the method you choose, it is important that the substrate system be set up and stocked properly, so education is a must.
ReefLion
I suggest you read the book mentioned by the previous poster, and read everything else you can get your hands on, including the many posts on this board on both topics, and then make your own informed decision. Regardless of the method you choose, it is important that the substrate system be set up and stocked properly, so education is a must.
ReefLion
One other thing, by the way. Since you are in Fairfax I would recommend a place call the Marine Scene, if you aren't aware of it already. It's out almost to Dulles Airport. The owner's name is Tom. He's a little busy, but he knows his stuff. I just moved away from the DC area, and I hope to stop back there every once in a while.
ReefLion
ReefLion
fwiw-a dsb and a plenum are really the same thing-with a different design...(imho)-if you can picture both being vertical, in profile(edge on-like your tank is standing on its short end), you can see why.
the dsb has water flowing on one side, while the plenum has flow on both sides.the main difference implied to me, is the different resulting 'zones' created in the bed.
look at the water as the bread in a 'sand sandwhich'.
the dsb would seem to be aerobic on one side-graduating to anaerobic towards the other.(the side touching the glass)
the plenum would seem to have the most anaerobic zone more towards the middle(since 02 is reaching it from the other side, too-'pushing the anaerobic zone further away, also.)
the question is then-what is the actual relative size and depth of the environmentally different sand zones between the two systems?and how much of the waste processing is each zone responsible for?
(this seems to me to be the best way of answering which one performs more efficiently- maybe a test should be done objectively comparing the two under 'identical' 75 gal.tanks?-=a middle of the road size aquarium=)
having said that-the dsb seems to be an excellent performer of waste processing in small closed systems-it's also more aesthetically pleasing to the eye,and it's less work to set up.the jaubert method(if my memory is correct)was initially designed and tested with/for fairly larger systems-like public aquariums-where the waste/biomass/gallonage parameters were proportionately different, as well.
both will work.
personally, i prefer the dsb-because it works fine,looks better (to me), and requires no special effort to set up
Nelliereefster- no flaming here, i'm asking 'cuz you seem so adamant, but -have you ever compared the two's performance physically in a true test?
admittedly i'm no expert on goemens-but does he provide analysis of actual 'zone spread' measurements in each type of system?and does he compare their performance under identical load/system size conditions?
(logic would imply (to me) that a dsb should have a proportionately larger anaerobic zone relative to its depth, since it has one less side exposed to water.....and that a nutrient sink is exactly what the purpose is-to soak up the nutrients-the hydrogen sulfide leaves the system-ultimately exporting the nutrients-or does goemens contend the sulfide keeps building up, ad infinitum?...it goes away to somewhere! it has to....)
the dsb has water flowing on one side, while the plenum has flow on both sides.the main difference implied to me, is the different resulting 'zones' created in the bed.
look at the water as the bread in a 'sand sandwhich'.
the dsb would seem to be aerobic on one side-graduating to anaerobic towards the other.(the side touching the glass)
the plenum would seem to have the most anaerobic zone more towards the middle(since 02 is reaching it from the other side, too-'pushing the anaerobic zone further away, also.)
the question is then-what is the actual relative size and depth of the environmentally different sand zones between the two systems?and how much of the waste processing is each zone responsible for?
(this seems to me to be the best way of answering which one performs more efficiently- maybe a test should be done objectively comparing the two under 'identical' 75 gal.tanks?-=a middle of the road size aquarium=)
having said that-the dsb seems to be an excellent performer of waste processing in small closed systems-it's also more aesthetically pleasing to the eye,and it's less work to set up.the jaubert method(if my memory is correct)was initially designed and tested with/for fairly larger systems-like public aquariums-where the waste/biomass/gallonage parameters were proportionately different, as well.
both will work.
personally, i prefer the dsb-because it works fine,looks better (to me), and requires no special effort to set up
Nelliereefster- no flaming here, i'm asking 'cuz you seem so adamant, but -have you ever compared the two's performance physically in a true test?
admittedly i'm no expert on goemens-but does he provide analysis of actual 'zone spread' measurements in each type of system?and does he compare their performance under identical load/system size conditions?
(logic would imply (to me) that a dsb should have a proportionately larger anaerobic zone relative to its depth, since it has one less side exposed to water.....and that a nutrient sink is exactly what the purpose is-to soak up the nutrients-the hydrogen sulfide leaves the system-ultimately exporting the nutrients-or does goemens contend the sulfide keeps building up, ad infinitum?...it goes away to somewhere! it has to....)
No flaming received. Yes, I have set-up and maintained both types of systems and the both do indeed have their own merits, but...
The statement that a plenum system has flow "on both isdes" is incorrect. It is a common misconception from the days of the undergravel filter, that water is being drawn thru a plenum, or that flow is being provided in some way to the isolated chamber under the sand.
This is not the case, and the plenum would not function at all if it were. The anoxic regoin below, in the chamber, is an environment where certain microbes, which cannot survive in an aerobic (oxygen rich) zone due to too high O2 concentration, flourish. These anoxic microbes are responsible for the reduction of nitrate to N2 gas. A plenum never achieves an anaerobic (oxygen free) zone.
A plenum allows an anoxic zone to develop from the top in, and from the bottom up, thereby increasing thickness of this highly desireable zone.
The DSB will produce the same anoxic zone, but it will be very thin and inefficient. What's more, below the anoxic zone in a DSB is an anaerobic zone where microbes do not use O2 to metabolize nutrients, and instead of producing inert compounds, produce hydrogen sulfide ( a noxious acidic gas, which is very detrimental to the tank inhabitants.
You are on track with the statement that DSBs tend to accumulate nutrients over time. No, that is not desireable since at some point, there must be an "export" If you've ever taken a DSB tank down to move, you'd agree that there was a pretty pungeant, nasty odor present in the bowels of the DSB. Since this is in contact with the water column, it will build up under operation and slowly start to leech H2SO4 into the water column (toxic to marine life and wreaks havoc on pH)
Next time you're on Amazon, look for the pamphlet I described above, it's cheap and a very informative read.
I'm in Fairfax too. Any frags for sale/trade out there????[/quote]
The statement that a plenum system has flow "on both isdes" is incorrect. It is a common misconception from the days of the undergravel filter, that water is being drawn thru a plenum, or that flow is being provided in some way to the isolated chamber under the sand.
This is not the case, and the plenum would not function at all if it were. The anoxic regoin below, in the chamber, is an environment where certain microbes, which cannot survive in an aerobic (oxygen rich) zone due to too high O2 concentration, flourish. These anoxic microbes are responsible for the reduction of nitrate to N2 gas. A plenum never achieves an anaerobic (oxygen free) zone.
A plenum allows an anoxic zone to develop from the top in, and from the bottom up, thereby increasing thickness of this highly desireable zone.
The DSB will produce the same anoxic zone, but it will be very thin and inefficient. What's more, below the anoxic zone in a DSB is an anaerobic zone where microbes do not use O2 to metabolize nutrients, and instead of producing inert compounds, produce hydrogen sulfide ( a noxious acidic gas, which is very detrimental to the tank inhabitants.
You are on track with the statement that DSBs tend to accumulate nutrients over time. No, that is not desireable since at some point, there must be an "export" If you've ever taken a DSB tank down to move, you'd agree that there was a pretty pungeant, nasty odor present in the bowels of the DSB. Since this is in contact with the water column, it will build up under operation and slowly start to leech H2SO4 into the water column (toxic to marine life and wreaks havoc on pH)
Next time you're on Amazon, look for the pamphlet I described above, it's cheap and a very informative read.
I'm in Fairfax too. Any frags for sale/trade out there????[/quote]
Nelliereefster-
so it's my understanding that the water layer underneath the sb is static?
(in which case it's really no different than a dsb-the sand just doesn't touch the glass directly, but still has one side completely anaerobic-the water has no exchange ability-due to lack of movement- it will start out anoxic, maybe for a short while-but cannot bring fresh O to keep from going anaerobic! it becomes a liquid 'extension' of the bottom zone of the sand bed...)
again-while running-the hydrogen sulfide does not stay in the dsb-it has to leave, and does, in very small amounts that leave the tank directly from the water column as gas bubbles,which, to date, have not caused any threat or discomfort to reef tank critters.little, if any, gets resorbed into the system.
(i have yet to see a dsb float up because a layer of gas built up!-the process happens slowly-may even be a true way of converting the tank to an 'open' system, in a sense-venting the end product to the atmosphere)
even a dsb that has 'soured' when kept anoxically(shutting a tank down,storing it in a closed bucket, etc.)will recover and function-leading me to believe that the 'anoxic danger' is not what many claim it to be.plus-the macro algaes grown in most dsb refugiums/sumps don't seem to evidence any H2SO4 distress-even in what should be a high H2SO4 environment according to the theory you support.
plus i have yet to see measurements of a study backing the claim that the anoxic zone is bigger in a plenum system than in a dsb of the same size.
it just seems to me that the advocates of the jaubert method seem to say that because one works,differently,that the other method is faulty, and one should switch.the majority of anecdotal observation seems to indicate otherwise.
a plenum also absorbs nutrients over time- it has to, simply by virtue of its being a habitat, and a physical media-at the very least-the mineral constituents of broken down fishpoops that work into the sand get incorporated there-plus the continual bacteria mortality(bacteria are always dying, and reproducing in the bed, and in the plenum-actually,everywhere in the system)
a plenum has no magic 'vacuum cleaner' that shoots the end products of initial waste breakdown into some 'black hole' that is lacking in a dsb.in any closed filter system, waste changes form, and maybe toxicity, but it must still be present, somewhere in the system, as something!
lastly-i think they accomplish the same end, just by different means-and i have never seen anything to indicate that a dsb is either below par, or a more inefficient method,or dangerous-under varied hobbyist situations.
so it's my understanding that the water layer underneath the sb is static?
(in which case it's really no different than a dsb-the sand just doesn't touch the glass directly, but still has one side completely anaerobic-the water has no exchange ability-due to lack of movement- it will start out anoxic, maybe for a short while-but cannot bring fresh O to keep from going anaerobic! it becomes a liquid 'extension' of the bottom zone of the sand bed...)
again-while running-the hydrogen sulfide does not stay in the dsb-it has to leave, and does, in very small amounts that leave the tank directly from the water column as gas bubbles,which, to date, have not caused any threat or discomfort to reef tank critters.little, if any, gets resorbed into the system.
(i have yet to see a dsb float up because a layer of gas built up!-the process happens slowly-may even be a true way of converting the tank to an 'open' system, in a sense-venting the end product to the atmosphere)
even a dsb that has 'soured' when kept anoxically(shutting a tank down,storing it in a closed bucket, etc.)will recover and function-leading me to believe that the 'anoxic danger' is not what many claim it to be.plus-the macro algaes grown in most dsb refugiums/sumps don't seem to evidence any H2SO4 distress-even in what should be a high H2SO4 environment according to the theory you support.
plus i have yet to see measurements of a study backing the claim that the anoxic zone is bigger in a plenum system than in a dsb of the same size.
it just seems to me that the advocates of the jaubert method seem to say that because one works,differently,that the other method is faulty, and one should switch.the majority of anecdotal observation seems to indicate otherwise.
a plenum also absorbs nutrients over time- it has to, simply by virtue of its being a habitat, and a physical media-at the very least-the mineral constituents of broken down fishpoops that work into the sand get incorporated there-plus the continual bacteria mortality(bacteria are always dying, and reproducing in the bed, and in the plenum-actually,everywhere in the system)
a plenum has no magic 'vacuum cleaner' that shoots the end products of initial waste breakdown into some 'black hole' that is lacking in a dsb.in any closed filter system, waste changes form, and maybe toxicity, but it must still be present, somewhere in the system, as something!
lastly-i think they accomplish the same end, just by different means-and i have never seen anything to indicate that a dsb is either below par, or a more inefficient method,or dangerous-under varied hobbyist situations.
I maintain that there is no difference between a 4" deep sandbed and a 3" sandbed over a 1" plenum.
Why?
For the sake of this discussion, let's assume that it takes 2" for your sandbed to go anaerobic, based on your grainsize, and the flow in your aquarium.
In the diagrams below, each carriage return/line represents 1 inch or so.
So for the sandbed, you have:
________________________
XXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXX
----------------------------------
And for the plenum you have:
_________________________
XXXXXXXXXXXXXXXXXXXXXX
-----------------------------------
-----------------------------------
Both have a 2" region of anaerobic water. In the DSB, this water is between sandgrains, while in the plenum system, the water is just underneath the plenum screen.
So please show me the substantial functional difference between the two?
I believe there is none. That's why I think a plenum is basically just necessary because some aquarists think it's a must to have some type of "mechanical device" to act as a filter. Then at least they have something to point to - in order to explain why their tank looks so nice. Pointing at a green, brown, and red pile of sand just isn't as satisfying...
Cheers
James Wiseman
Why?
For the sake of this discussion, let's assume that it takes 2" for your sandbed to go anaerobic, based on your grainsize, and the flow in your aquarium.
In the diagrams below, each carriage return/line represents 1 inch or so.
So for the sandbed, you have:
________________________
XXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXX
----------------------------------
And for the plenum you have:
_________________________
XXXXXXXXXXXXXXXXXXXXXX
-----------------------------------
-----------------------------------
Both have a 2" region of anaerobic water. In the DSB, this water is between sandgrains, while in the plenum system, the water is just underneath the plenum screen.
So please show me the substantial functional difference between the two?
I believe there is none. That's why I think a plenum is basically just necessary because some aquarists think it's a must to have some type of "mechanical device" to act as a filter. Then at least they have something to point to - in order to explain why their tank looks so nice. Pointing at a green, brown, and red pile of sand just isn't as satisfying...
Cheers
James Wiseman
Okay, this may be a long technical read but please read it all the way through. I'm a mechanical engineer with a minor in organic chemistry, just for qualification's sense.
There appears to be misunderstanding on the technical side of things.
With a DSB, asuming 4 inches in depth and a grain size on the order of 1.0-1.5 mm, it will reach the point of anaerobia at about the 2 inch mark, give or take. Below his layer, the sand bed is devoid of appreciable (measureable) dissolved oxygen. The target layer (i.e. the layer that is responsible for reduction of nitrate into N2 gas) is the anoxic region (a region LOW in O2 but NOT devoid. This is an important point because the specific microbes (bacteria) that are responsible for nitrate metabolism can only survive in a low O2 environment. Think of it as a "niche" environment.
In the DSB, this "niche" is only a few mm's thick. Here inlies the efficiency part. More on that in a moment... As we move deeper into the DSB, we pass through the anoxic (low O2) regoin and achieve anaerobia. This is a static zone where no flow due to water kinetics occurs. Pumps and powerheads cannot "force" water to move this deep into the sand bed. Is there absolutely no molecular motion here? Answer, no, there is in fact motion but it is a result of molecular diffusion and the driving force is molecular charge differential. Some molecules carry a net positive or negative charge and throughout the sand bed, different layers are net positive or net negative (like attracts dislike and repels like) + repels + but attracts - charged molecules.
A point of order: Since this is a restrictive matrix of fine grained aragonite, this motion (diffusion) is greatly slowed, and takes a great deal of time to reach a steady state, if it ever does. What I mean is: The accumulation of organic waste occurs at a rate faster than this type of matrix can metabolize the input and convert it to inert molecules like N2 gas.
So, from top to bottom of a sand bed, the ammonia cycle starts by ammonia being metabolized to nitrite then nitrate all in the aerobic zone (maybe 1 inch thick. As we pass deper, we encounter the anoxic zone, and here is where nitrate is converted to N2 gas and diffused out into the water column in the opposite direction (up) due mainly to bouyancy and sand-stirrers releasing a path for it to escape. Below he anoxiv regoin, we encounter the anaerobic region where nutrients (nitrate, sulfate, phosphorous, organic molecules, etc...) that were not converted in the thin inefficient anoxic region to inert compounds, tend to accumulate over time.
How does this cause problems. Well, it doesn't cause the kind of catastrophic problems we imagine like a sea apple death, or a pH crash. Bt, over ime it leands itself towards pH instability. Sulfurous compounds are also a poison. Albeit they diffuse in small quantities, they ae harmful. It is analogous to sipping mercury laden water. It won't kill you today, tomorow or next month, bt wait a few years. And "years" is the timeframe we're driving at for system stability.
Now the plenum. If you read any part of this post, read this twice and digest it. Where the DSB stops being anoxic and becomes anaerobic is where then plenum architecture comes into play. Ideally, the 3-4 inches above he water void has a mirror image of anoxia. That is, we move from aerobia to anixia, but not to anaerobia, rather anoxia continues all the way down throug the wate layer. It's a 1-2 inch thick anoxic layer -MUCH more efficient, and prevents build up of nutrients, thereby promoting LONG TERM stability.
As a matter of scale, natural reefs ecosystems can get by with a DSB and minute anoxic regoin because lower amounts of nutrients are spread over a huge surface area. In a closed system, we do not have the space to make this happen.
Finally, I'm not saying a DSB won't work. I am saying that there are significant differences between a DSB and a plenum system. Like all of you, I believe hard facts, and there is a mountain of bullshit afloat in this hobby, rom people who profess to be experts. I am by far, no expert. But the science of this has me convinced. And, my experience with both type of systems leads me (by data) to favor the plenum system.
So what if it takes a little more to construct and set up. Long term, it's worth it.
There appears to be misunderstanding on the technical side of things.
With a DSB, asuming 4 inches in depth and a grain size on the order of 1.0-1.5 mm, it will reach the point of anaerobia at about the 2 inch mark, give or take. Below his layer, the sand bed is devoid of appreciable (measureable) dissolved oxygen. The target layer (i.e. the layer that is responsible for reduction of nitrate into N2 gas) is the anoxic region (a region LOW in O2 but NOT devoid. This is an important point because the specific microbes (bacteria) that are responsible for nitrate metabolism can only survive in a low O2 environment. Think of it as a "niche" environment.
In the DSB, this "niche" is only a few mm's thick. Here inlies the efficiency part. More on that in a moment... As we move deeper into the DSB, we pass through the anoxic (low O2) regoin and achieve anaerobia. This is a static zone where no flow due to water kinetics occurs. Pumps and powerheads cannot "force" water to move this deep into the sand bed. Is there absolutely no molecular motion here? Answer, no, there is in fact motion but it is a result of molecular diffusion and the driving force is molecular charge differential. Some molecules carry a net positive or negative charge and throughout the sand bed, different layers are net positive or net negative (like attracts dislike and repels like) + repels + but attracts - charged molecules.
A point of order: Since this is a restrictive matrix of fine grained aragonite, this motion (diffusion) is greatly slowed, and takes a great deal of time to reach a steady state, if it ever does. What I mean is: The accumulation of organic waste occurs at a rate faster than this type of matrix can metabolize the input and convert it to inert molecules like N2 gas.
So, from top to bottom of a sand bed, the ammonia cycle starts by ammonia being metabolized to nitrite then nitrate all in the aerobic zone (maybe 1 inch thick. As we pass deper, we encounter the anoxic zone, and here is where nitrate is converted to N2 gas and diffused out into the water column in the opposite direction (up) due mainly to bouyancy and sand-stirrers releasing a path for it to escape. Below he anoxiv regoin, we encounter the anaerobic region where nutrients (nitrate, sulfate, phosphorous, organic molecules, etc...) that were not converted in the thin inefficient anoxic region to inert compounds, tend to accumulate over time.
How does this cause problems. Well, it doesn't cause the kind of catastrophic problems we imagine like a sea apple death, or a pH crash. Bt, over ime it leands itself towards pH instability. Sulfurous compounds are also a poison. Albeit they diffuse in small quantities, they ae harmful. It is analogous to sipping mercury laden water. It won't kill you today, tomorow or next month, bt wait a few years. And "years" is the timeframe we're driving at for system stability.
Now the plenum. If you read any part of this post, read this twice and digest it. Where the DSB stops being anoxic and becomes anaerobic is where then plenum architecture comes into play. Ideally, the 3-4 inches above he water void has a mirror image of anoxia. That is, we move from aerobia to anixia, but not to anaerobia, rather anoxia continues all the way down throug the wate layer. It's a 1-2 inch thick anoxic layer -MUCH more efficient, and prevents build up of nutrients, thereby promoting LONG TERM stability.
As a matter of scale, natural reefs ecosystems can get by with a DSB and minute anoxic regoin because lower amounts of nutrients are spread over a huge surface area. In a closed system, we do not have the space to make this happen.
Finally, I'm not saying a DSB won't work. I am saying that there are significant differences between a DSB and a plenum system. Like all of you, I believe hard facts, and there is a mountain of bullshit afloat in this hobby, rom people who profess to be experts. I am by far, no expert. But the science of this has me convinced. And, my experience with both type of systems leads me (by data) to favor the plenum system.
So what if it takes a little more to construct and set up. Long term, it's worth it.
Glancing at diplomas...nah...
Buildup of the deadly poisonous toxic hydrogen sulfide has already been debunked about 1 x 10^6 times. It's a myth.
Secondly, how can a plenum be MORE efficient than a DSB. If a DSB reduces N compounds to below-threshold levels can you do better than that? Nope. With a plenum, you have a useless inch of barren "non-habitat" whereas with a DSB, that space is inhabited by not just SRB's but actual macro-fauna.
Interesting thread indeed! You wouldn't happen to be French would you Nellie? The plenum is still pushed very hard in Europe, whereas Americans have moved on.
Cheers
James
Buildup of the deadly poisonous toxic hydrogen sulfide has already been debunked about 1 x 10^6 times. It's a myth.
Secondly, how can a plenum be MORE efficient than a DSB. If a DSB reduces N compounds to below-threshold levels can you do better than that? Nope. With a plenum, you have a useless inch of barren "non-habitat" whereas with a DSB, that space is inhabited by not just SRB's but actual macro-fauna.
Interesting thread indeed! You wouldn't happen to be French would you Nellie? The plenum is still pushed very hard in Europe, whereas Americans have moved on.
Cheers
James
Please clarify: Where does the anoxic microbs colonize on? Do they float freely in the plenum? Or do they have to be attached (colonized) on some type of subtrate?
I am in no means scientist of any kind as you can probably tell from the terms I used, so please fill in the correct terms for me anytime.
My question is, if the microbs responsible for metabolizing NO3 into N2 has to be colonized on surfaces, wouldn't DSB a more suitable instead as the sand grains provided such surface area for them to colonize on. I would assume yes as that's the general idea of placing bioballs in the coil denitrator.........for bacteria to colonize upon.
IF that's the case, wouldn't 1" or 2" below the plenum be an inefficient use of space?
I am in no means scientist of any kind as you can probably tell from the terms I used, so please fill in the correct terms for me anytime.
My question is, if the microbs responsible for metabolizing NO3 into N2 has to be colonized on surfaces, wouldn't DSB a more suitable instead as the sand grains provided such surface area for them to colonize on. I would assume yes as that's the general idea of placing bioballs in the coil denitrator.........for bacteria to colonize upon.
IF that's the case, wouldn't 1" or 2" below the plenum be an inefficient use of space?
Nellie,
What you seem to be saying is that a 2.5" DSB would be fine, but a 4" DSB is not because it collects noxious compounds. Everything down to the 2.5" layer, by your reckoning, seems to be ok. Even assuming that is correct, it seems to me that top 2.5" (or 2.1" or whatever you would declare it to be) is working just fine to reduce NO3. As James noted, you can't do better than zero.
Your issue seems to be a purported lower layer that collects all sorts of things. The problem with this, in my mind, is that it ignores the action of the many fauna that inhabit a properly-seeded DSB. Worms and other creatures clearly go beyond the 3-4" level in a DSB, working the sand and slowly moving water through it.
May I ask the date of the Goeman's reference you are relying on? Also, are you drawing support from sources other than that pamphlet? I recall reading a number of anecdotal reports of plenum systems undergoing crashes over time, either through disruption of the layers or simply to the collection of the very things you say only reside in DSB's. I'm curious if you've read any of the same reports.
ReefLion
What you seem to be saying is that a 2.5" DSB would be fine, but a 4" DSB is not because it collects noxious compounds. Everything down to the 2.5" layer, by your reckoning, seems to be ok. Even assuming that is correct, it seems to me that top 2.5" (or 2.1" or whatever you would declare it to be) is working just fine to reduce NO3. As James noted, you can't do better than zero.
Your issue seems to be a purported lower layer that collects all sorts of things. The problem with this, in my mind, is that it ignores the action of the many fauna that inhabit a properly-seeded DSB. Worms and other creatures clearly go beyond the 3-4" level in a DSB, working the sand and slowly moving water through it.
May I ask the date of the Goeman's reference you are relying on? Also, are you drawing support from sources other than that pamphlet? I recall reading a number of anecdotal reports of plenum systems undergoing crashes over time, either through disruption of the layers or simply to the collection of the very things you say only reside in DSB's. I'm curious if you've read any of the same reports.
ReefLion
No, not french, but I speak japanese and spanish, so perhaps it is the "ole' " in me that so defends the plenum.
To answer the anoxic/grain surface area Q. The void isn't dead space but a means by which the anoxic regon is extend further (thicker) into the substrate from top down and from void up. Yes, they develop a bio-film on the substrate.
Once a plenum is "established" (usually 2-3 months after set-up) It should not be overly disturbed by agitation. Remember, you're trying to maintain the anoxic-ness of he lower layer(s)
I think your statement that "Americans have moved on" isn't entirely accurate. In California, it is the standard, still, as well as here in Fairfax (Marine Scene) :lol: :lol: :lol:
Anyway, I shot my wad. But good thread. Worth a little more debate obviously
To answer the anoxic/grain surface area Q. The void isn't dead space but a means by which the anoxic regon is extend further (thicker) into the substrate from top down and from void up. Yes, they develop a bio-film on the substrate.
Once a plenum is "established" (usually 2-3 months after set-up) It should not be overly disturbed by agitation. Remember, you're trying to maintain the anoxic-ness of he lower layer(s)
I think your statement that "Americans have moved on" isn't entirely accurate. In California, it is the standard, still, as well as here in Fairfax (Marine Scene) :lol: :lol: :lol:
Anyway, I shot my wad. But good thread. Worth a little more debate obviously
The Geoman's pamphlet is one data point others include discussions with LFS owners in Cali, and propogators there, as well in Japan (Okinawa) Other boards (blasphemy!!) offer good things to say about plenums, and tens years at the game has convinced me that the plenum works, beyond what the DSB can do.
H2SO4 is but one of the "byproducts" of incomplete reduction in a DSB. Carbonic acid and methane are also produced in the anaerobic zone. None of which can be called a beneficial trace element.
Let's keep the thread going, very good stuff and I'm listening to everyone, Just not convinced...
Nellie
H2SO4 is but one of the "byproducts" of incomplete reduction in a DSB. Carbonic acid and methane are also produced in the anaerobic zone. None of which can be called a beneficial trace element.
Let's keep the thread going, very good stuff and I'm listening to everyone, Just not convinced...
Nellie
Yes, Bob Goemans recommends vacuuming areas where detritus collects once a month and every two to three months vacuum the entire sandbed, but only going down 1/2 to 1 inch. Bob Goemans also states that Dr. Jaubert recommends to leave 75% of the sandbed unobstructed by rock.
I personally would have a hard time siphoning under all my live rock even if most of it was elevated, so I went with a DSB. I'm lazy though :wink: .
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