luther1200
Premium Member
So its possible, but unlikely if the tank is well maintaned?
DSB Diagram -- Seeking Consensus
- Thread starter Whys
- Start date
jenglish
Marquis de Carabas
I think if well maintained a DSB should last many many years. If I move a tank it is generally advisable to go ahead and replace the sand instead of moving it. My sand was reused and is about 3 years old and is still ok. I would say if we were looking at infinite lifespan then eventually any SB would get loaded. I think a SB that is cleaned and has decent nutrient export it should be Ok for years and years. Sorry I keep dancing around a direct answer here
I don't generally worry about my sand becoming loaded, but I am wanting to install a rock lift and would likely use fresh sand when I put sand back in.
I think phosphate will stick to the rock if the rock is exposed to high levels of phosphate. It will equilibriate with the water overtime. So if the water is low in PO4 ,the rock will eventually get there. If the water is low in PO4 from the begriming ,there wont be much if any on the rock.
luther1200
Premium Member
I am trying to make a comparison of LR and LS. IMO if you say PO4 will bind to the sand it would also have to bind to the LR. And to say that a DAB will become loaded with PO4 over time, logically is saying that LR will become loaded with PO4 over time. Which I'm not saying is impossible, but if the tank is well maintained I don't think it would happen.
Now how about Hydrogen Sulfide. That is also an effect from not properly maintaining a DSB, right? It is not definitely going to happen to every DSB? Only if you get a build up of nutrients. Or do I have that wrong? I do think its worth mentioning the possibilities of these things that can happen, but it should be made clear as to why they happen. Or at least a very brief generalized explanation of why.
Now how about Hydrogen Sulfide. That is also an effect from not properly maintaining a DSB, right? It is not definitely going to happen to every DSB? Only if you get a build up of nutrients. Or do I have that wrong? I do think its worth mentioning the possibilities of these things that can happen, but it should be made clear as to why they happen. Or at least a very brief generalized explanation of why.
jenglish
Marquis de Carabas
Chemically speaking LR and LS have equal chance of absorbing PO4. It is really gravity that makes the difference. The detritus settles on the sand and begins breaking down. If you were to not blow out the holes in your LR every once in a while the same thing is happening. I can't honestly say that I have kept a tank long enough to get to PO4 saturation of sand but I have seen threads of sand beds hitting this point. In poorly maintained tanks it happens quickly, in a well maintained bed I think it should take a long time. Unfortunately testing for PO4 in sand or rock can't be done directly and I would think require moving it into new SW and giving it time to leach to see if you got a reading, so not something practical to test.
As far as hydrogen sulfide I was always under the impression that it was linked to sand bed depth and true anoxic conditions rather than nutrient buildup. I could be wrong on that though.
As far as hydrogen sulfide I was always under the impression that it was linked to sand bed depth and true anoxic conditions rather than nutrient buildup. I could be wrong on that though. posted by jenglish.
It's linked to both anoxia and nutrrient availability.. The heterotrophic bacteria need organic carbon. phosphorous ,a source of nitrogen and oxygen for energy. In an anoxic zone without any nutrients they won't grow at all. In an anoxic zone(no nitrate or other source of oxygen) with nutrients they will turn to the oxygen in sulfate(SO4) creating hyudrogen sulfide as a by product.
(SO4)
It's linked to both anoxia and nutrrient availability.. The heterotrophic bacteria need organic carbon. phosphorous ,a source of nitrogen and oxygen for energy. In an anoxic zone without any nutrients they won't grow at all. In an anoxic zone(no nitrate or other source of oxygen) with nutrients they will turn to the oxygen in sulfate(SO4) creating hyudrogen sulfide as a by product.
(SO4)
luther1200
Premium Member
So in a SSB you won't run into that problem?
luther1200
Premium Member
Is there a "clear" depth at which these different layers happen?
Here is a study which concludes: no significant difference in denitrification at depths beyond 2 inches up as well as no significant difference if a plennum is used or with variable grain size. These experiments , however, did not include benthic fauana in the test tanks.
http://www.advancedaquarist.com/2005/6/aafeature#h5
http://www.advancedaquarist.com/2005/6/aafeature#h5
luther1200
Premium Member
Thanks
Whys
New member
First draft
First draft
To better understand the anatomy of a deep sand bed, let us first look at a shallow sand bed.
In a shallow sand bed, detritus (waste) and other organic matter is first eaten by the clean up crew of crabs, stars, hermits, and snails. The smaller particulates they produce are then further broken down by copepods, other benthic organisms, and worms. The remaining dissolved organics are then converted by the "nitrifying" bacteria, from ammonium (toxic), to nitrite (less toxic), to nitrate (least toxic). All of this takes place within a layer of sand oxygenated by moving water, termed oxic, and the bacteria there require oxygen to live, thus are termed aerobic. In a shallow sand bed this is where the process ends. The nitrate simply accumulates in the water column to be removed by ritual water change.
In a deep sand bed, there are another type of bacteria, termed anaerobic, that require a depleted oxygen environment to live. Among these are the "denitrifying" bacteria that will convert toxic nitrate into beneficial nitrogen. The primary objective of a deep sand bed is to provide a layer of very low oxygen, termed hypoxic, where bacteria can function anaerobically. The potential harm is in creating a layer completely devoid of oxygen, termed anoxic, where "reducing" bacteria can convert sulfate into hydrogen sulfide. This and other toxins can dangerously accumulate in a sand bed that is too deep or not properly maintained.
It is important to point out that the full benefits and challenges surrounding deep sand beds are still a matter of some debate and the conversation is often confused by competing terminology. Because denitrification only occurs at the very bottom of the hypoxic layer, environmentalists often borrow the term anoxic (labeled in blue) to mean extremely hypoxic. This of course requires another borrowed term, anaerobic (labeled in blue), to mean truly anoxic.*
Here are some general rules of thumb for maintaining a deep sand bed. It should be at least four inches deep but no more than six, consisting mostly of fine grains, sometimes called "oolite" or "sugar-fine". Keep the benthic and worm populations healthy by avoiding Sand-Sifting stars, most crabs, and limiting hermits. If possible and as needed, occasionally rejuvenate these populations with fresh liverock or true livesand from a well established aquarium, as this may be key to long term success. Do not disturb the sand bed. It should not be vacuumed clean or carelessly displaced, but Brittle and baby stars, as well as Nassarius and Cerith snails, provide a slow and beneficial agitation of the sand. Remember, a deep sand bed is a living thing that must be kept in careful balance.
Rules of Thumb
- 4" to 6"; fine-grain; do not vacuum or disturb.
- Helpful: Brittle & baby stars, Nassarius & Cerith snails.
- Unhelpful: Sand-Sifting stars, most crabs, too many hermits.
- Rejuvenate worm and benthic populations for long term success.
* Why anaerobic for truly anoxic? As it happens, the denitrifying bacteria are not truly anaerobic, but are aerobic bacteria functioning in an anaerobic manner, thus environmentalists call them "facultative" (labeled in blue). Because only the "reducing" bacteria in the truly anoxic layer are truly anaerobic, environmentalists have borrowed the term anaerobic to mean truly anoxic.
First draft
To better understand the anatomy of a deep sand bed, let us first look at a shallow sand bed.
In a shallow sand bed, detritus (waste) and other organic matter is first eaten by the clean up crew of crabs, stars, hermits, and snails. The smaller particulates they produce are then further broken down by copepods, other benthic organisms, and worms. The remaining dissolved organics are then converted by the "nitrifying" bacteria, from ammonium (toxic), to nitrite (less toxic), to nitrate (least toxic). All of this takes place within a layer of sand oxygenated by moving water, termed oxic, and the bacteria there require oxygen to live, thus are termed aerobic. In a shallow sand bed this is where the process ends. The nitrate simply accumulates in the water column to be removed by ritual water change.
In a deep sand bed, there are another type of bacteria, termed anaerobic, that require a depleted oxygen environment to live. Among these are the "denitrifying" bacteria that will convert toxic nitrate into beneficial nitrogen. The primary objective of a deep sand bed is to provide a layer of very low oxygen, termed hypoxic, where bacteria can function anaerobically. The potential harm is in creating a layer completely devoid of oxygen, termed anoxic, where "reducing" bacteria can convert sulfate into hydrogen sulfide. This and other toxins can dangerously accumulate in a sand bed that is too deep or not properly maintained.
It is important to point out that the full benefits and challenges surrounding deep sand beds are still a matter of some debate and the conversation is often confused by competing terminology. Because denitrification only occurs at the very bottom of the hypoxic layer, environmentalists often borrow the term anoxic (labeled in blue) to mean extremely hypoxic. This of course requires another borrowed term, anaerobic (labeled in blue), to mean truly anoxic.*
Here are some general rules of thumb for maintaining a deep sand bed. It should be at least four inches deep but no more than six, consisting mostly of fine grains, sometimes called "oolite" or "sugar-fine". Keep the benthic and worm populations healthy by avoiding Sand-Sifting stars, most crabs, and limiting hermits. If possible and as needed, occasionally rejuvenate these populations with fresh liverock or true livesand from a well established aquarium, as this may be key to long term success. Do not disturb the sand bed. It should not be vacuumed clean or carelessly displaced, but Brittle and baby stars, as well as Nassarius and Cerith snails, provide a slow and beneficial agitation of the sand. Remember, a deep sand bed is a living thing that must be kept in careful balance.
Rules of Thumb
- 4" to 6"; fine-grain; do not vacuum or disturb.
- Helpful: Brittle & baby stars, Nassarius & Cerith snails.
- Unhelpful: Sand-Sifting stars, most crabs, too many hermits.
- Rejuvenate worm and benthic populations for long term success.
* Why anaerobic for truly anoxic? As it happens, the denitrifying bacteria are not truly anaerobic, but are aerobic bacteria functioning in an anaerobic manner, thus environmentalists call them "facultative" (labeled in blue). Because only the "reducing" bacteria in the truly anoxic layer are truly anaerobic, environmentalists have borrowed the term anaerobic to mean truly anoxic.
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jenglish
Marquis de Carabas
I will say there are two schools of thought on cleaning your DSB. Some say don't do it and others say do it weekly. I know folks from both camps that have had succes. Those who deep clean to the bottom do not do it all at once but in weekly sections so not to eliminate and beneficial fauna
jenglish
Marquis de Carabas
thats an interest read. Those depth numbers were in cm so it was closer to a 1 inch and 3.5 inch bed. It's hard to belive denitrification was happening in a 1 inch bed.
Now if I can just convince the Mrs to let me set up 24 tanks to replicate it..... can I sleep on somebody's couch? :lol:
Glad you liked it.
I think shallow beds do unquestionably perform denitrification. Deeper sand all by itself (such as the very deep sand in a bucket bed ) may not do anything beyond the first inch or two since nothing of value to the bacteria will penetrate very deeply without some force to move it, in my opinion.
This study was pretty well done , though no benthic fauna were in play. If they were and transported organic carbon and chaneled the deeper beds, I suspect those beds would have had more denitrification just becasue there is more sand. I would be reluctant to state that a bed needs to be 4 to 6 inches to denitrify, however.That 4 to 6 inch notion and interminable grain size arguments are pretty old school,now, and may go the way of the plennum design. Many run sucessfull low nutrient reefs without any sand in them at all.
I think shallow beds do unquestionably perform denitrification. Deeper sand all by itself (such as the very deep sand in a bucket bed ) may not do anything beyond the first inch or two since nothing of value to the bacteria will penetrate very deeply without some force to move it, in my opinion.
This study was pretty well done , though no benthic fauna were in play. If they were and transported organic carbon and chaneled the deeper beds, I suspect those beds would have had more denitrification just becasue there is more sand. I would be reluctant to state that a bed needs to be 4 to 6 inches to denitrify, however.That 4 to 6 inch notion and interminable grain size arguments are pretty old school,now, and may go the way of the plennum design. Many run sucessfull low nutrient reefs without any sand in them at all.
Whys
New member
I don't feel I can provide this diagram and explanation without some kind of depth recommendation. Your final statement would seem to suggest one can have a DSB in a bare-bottom tank. That won't go far to improve comprehension. :]
Is the 4 to 6 inch rule of serious question? I ask that sincerely. I have a 5 inch DSB in my display and it seems to be working, but I can't say that conclusively just yet.
therealfatman
In Memoriam
Oooops double post.
therealfatman
In Memoriam
The Toonen article posted is very limited and really not a definite study. Other articles have shown that the transport of nutrients and the increase in oxygen at deeper levels is increased as a result of increased water velocity and especially as a result of increased water velocity and subtrate surfaces that are rippled. Many test show pore water exchange is increased due to larger particle sizes.
These areas of study (velocities and surface shape of beds) were not included in the tests/research and as the other studies showed nutrient transport into fine sediments of sand beds in excess of 3 inches and oxygen to I believe 1.5 inches show that sand deeper than 2 inches might still be beneficial and equally or more effective. Without ripples or some disturbance of the flat surface of a deep sand bed the depth of oxygen and nutrients caused by water movement or diffusion is dismal so Toonens results make some sense, because if only diffusion is responsible for the transport of oxygen and nutrients 2 inches makes sense. The Toonen tests I assume (based upon photos) used a nearly flat bed of sand and the power heads contribution to water velocity over the sand bed is not even apparently measured or even considered. By appearance the sand bed surfaces from tank to tank do not really even seem to match. As the surface shape/conditions can have a great deal to do with the movement of water and oxygen deeper into the substrate this also brings questions to the tests. A test of such limited scope and running a mere two months seems a bit short to base a "new school" conclusion upon. Especially when addressing something like plenums. Also not addressed was the effect of critters as mentioned by another poster. The tunnels created by critters can greatly increase the sandbed depths of nutrients and oxygen brought about by high water velocities.
I do not believe the test posted should be consider as being definitive or conclusive. Just another opinion based on a study that was limited in scope and duration.
These areas of study (velocities and surface shape of beds) were not included in the tests/research and as the other studies showed nutrient transport into fine sediments of sand beds in excess of 3 inches and oxygen to I believe 1.5 inches show that sand deeper than 2 inches might still be beneficial and equally or more effective. Without ripples or some disturbance of the flat surface of a deep sand bed the depth of oxygen and nutrients caused by water movement or diffusion is dismal so Toonens results make some sense, because if only diffusion is responsible for the transport of oxygen and nutrients 2 inches makes sense. The Toonen tests I assume (based upon photos) used a nearly flat bed of sand and the power heads contribution to water velocity over the sand bed is not even apparently measured or even considered. By appearance the sand bed surfaces from tank to tank do not really even seem to match. As the surface shape/conditions can have a great deal to do with the movement of water and oxygen deeper into the substrate this also brings questions to the tests. A test of such limited scope and running a mere two months seems a bit short to base a "new school" conclusion upon. Especially when addressing something like plenums. Also not addressed was the effect of critters as mentioned by another poster. The tunnels created by critters can greatly increase the sandbed depths of nutrients and oxygen brought about by high water velocities.
I do not believe the test posted should be consider as being definitive or conclusive. Just another opinion based on a study that was limited in scope and duration.
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