Are Deep Sand Beds, DSBs, dangerous to use in a marine aquarium?

[jda]

I can tell you from from personal experience that silica can easily handle nitrates, but phosphates will be an issue. I have never had detectable phosphates in a tank with aragonite sand since Salifert test kits came out, but I have with silica. I also never had silica sand leech silica into the water.

I think that you all assume that once the organics are in the sand that they cannot leave. Vacuuming leaves them, but they can also turn into bacteria, microfauna, pods, fish food, poop and then out the skimmer. I am not all Dr. Ron "never touch the sand bed" kind of equilibrium but the phosphates are handled enough to never be detectable.

 

[Fredfish]

... Do your maintenance (tidal flushing) and grow some nice corals or try the no maintenance routine and have a nice marsh full of detrital sediment build up

There is reasonable evidence that there are more possible outcomes than those two.

 

[asylumdown]

I've been following this thread for a while, and I would tend to agree with the camp that the diagram of the global phosphorous cycle is a poor analogy for what happens in aquariums. The issue is the scale at which these processes are taking place. While it is true that P is eventually sequestered in deep sea sediments, the sand beds in our tanks cannot and will not ever resemble, under any circumstances, deep sea conditions. There is a drastic change in P concentrations in sea water from the surface to the deep sea, and the processes that sequester P permanently in the deep ocean are as much a function of the different processes occurring at different depths over vast amounts of space and time as they are anything else. Suggesting that a deep sand bed, which at best simulates a few square feet of the top 4-6 inches of substrate of a shallow bay, lagoon, or tidal pool, in a time scale measured at most in decades (but usually much less) operates anything at all like the deep ocean on a time scale measured in millennia, from a physical or biotic point of view, is stretching it by a mile.

Also, while yes it is true that phosphate can bind directly to the surface of aragonite, this process is not irreversible. Phosphate binds best to aragonite in sea water at a pH of around 8.4. If the aragonite crystals are not growing and trapping the P inside the structure of the mineral itself, the P is free to be liberated either by a drop in pH, or a change in the equilibrium concentrations. I've not read any articles on the pH gradient present within a DSB, but I would hazard a guess that the pH in the anoxic zone is not the same as the display tank at large. It's very possible that the pH within a DSB is not favourable for the adsorption of P to the surface of calcium carbonate, and regardless if you run your tank at a lower pH you can actually quite easily encourage the liberation of P from calcium carbonate or at least make it a non-significant source of P sequestration. It's one of the reasons that Randy Holmes-Farley suggests running tanks at a higher pH or dosing with limewater as it discourages the release of P from rocks and sand that is possible at a lower pH

Further, if the aragonite crystal is indeed growing, which is possible under a variety of circumstances present in home aquariums, the aragonite does in fact have an inexhaustible capacity to bind and sequester P. As the crystal grows, P gets incorporated right in to the crystal structure, and more binding sites for P are created.

So while yes, the P in a DSB does not get easily converted to gas like nitrogen does, it does not mean that it's always trapped there forever. Assuming the bed is working as it should, and that all solid waste is broken down to the point where it's soluble again, it will either get taken up by something else, or eventually exported from the system by the skimmer or some sort of phosphate binding media.

Saying that calcium carbonate (be that rocks or sand) is permanent sink for P that eventually "fills up" in any aquarium ignores the more nuanced relationship between the different forms of orthophosphate and their propensity to be adsorbed, pH, and relative concentrations. There are conditions where it is true, but there are lots of other conditions where it is not.

 

[Reefin' Dude]

I do not pretend to be a biologist or chemist, nor to have any insights into any of this. I have two comments/questions:

1) the global phosphate cycle, while important to learn, is NOT going on in our tanks. The differences between the macro and micro level are too much to just assume that the global cycle occurs on a smaller scale in our tanks.

no, but the basics do. a fair amount of the process is going on in our systems. are you saying that the reef hobby industry is finally realizing that our systems are not imitating nature? i thought that was the whole argument for having a DSB in the first place? which is it?

2) the phosphate sink theory seems to rely heavily on gravity bringing nutrients downward. Why isn't it possible that bacteria that incorporate the phospahate flow back into the water column? Or the plankton? Or the pods as they get eaten by fish, and pooped back into the water column, etc. I have no knowledge of this, just asking a question.

it is not wise to not believe in gravity. the equilibrium reaction can be capable of pulling against gravity for dissolved P, but not for the solid forms. if what you say is true, then we would see this occurring, we would see an export of material up and out of the substrate. we do not.

3) the "everything poops" theory seems to rely on solid poop. Do we know what snail poop, worm poop, crab poop, etc look like? Are they solid or liquid, flowing back into the water column? Again, I have no knowledge, just asking a question.

it doesn't matter. if the organisms is in the substrate, than it releases waste in the substrate. it is all of this various critter waste that is feeding other organisms. no waste, no organisms. this right there shows that a substrate is increasing in nutrients.

One final comment: the "you must flush your toilet" or "take out the garbage" comparison fails because proponents of DSBs are trying to create a recycling ecosystem--the same is not true of our houses. On a small scale, some people attempt similar limited cycles in our houses--houses with septic systems and wells recycle their liquid wastes. Compost bins recycle unused nutrients that we bring into our houses.

i am not sure you understand how a septic or well works. septic systems can get clogged and need cleaning. they are not closed systems. they have drain lines also. what does one do with the compost?

Sorry, thought of a couple more comments:

1) someone mentioned earlier about focusing on the organisms we want in our tanks, and not trying to support an entire ecosystem to help support the other organisms. For me, a "live" sand bed IS one of the organisms I want to keep. For me, it's more than just a filter like my skimmer, it's a cool, living thing. I get just as much enjoyment looking at a worm trail or a nitrogen bubble as my wife gets from watching the yellow tang. (I am sure there are some people reading this that get just as much excitement from watching their skimmer--but we will leave that for another thread)

nobody is saying to get rid of the substrate, just to understand what is going on inside of it and adapt the maintenance schedule of it to match the trophic level the aquarist is trying to emulate in the system. if the substrate is a must have critter for you, then keep it, but just know what is necessary to keep it alive and healthy just like you would any other organism.

2) the entire discussion on this thread has been about P. Can we then conclude that a DSB DOES work effectively on the N cycle? Indefinitely? Safely? If I run phosphate reducer with a DSB, is that a safe and complete system (recoginizing of course that there are other ways to have a complete and safe system; and that there are other components like WC and skimmer, etc).

because they are tied together. bacteria need P in order to process N. bacteria are living organisms. all organisms need P. you can not use one without the other. the same goes for H and C.

3) I apologize in advance if this belongs in the noob forum: I am still trying to figure out the correct way to plumb a rabbit into my system. Should I use a deep substrate bed in his cage, or shallow? Bare bottom? Are there certain species of rabbit better at de-phosphatization than others? Thanks in advance for your help.

in a BB system, the entire herbivorous and decomposition food chain is removed. the aquarist is all of these. the point in BB system is to trap the detritus in an easy to clean area. then remove the detritus as often as necessary to maintain the wanted trophic level of the systems. i am a big fan of the conical settling tank.

It is entirely reasonable to ask what mechanisms there might be to bring nutrients like P back up into the water column. Bacteria can be mobile. I don't know if they are in the sand bed.

i have yet to see a P cycle graphic showing more/larger arrows upwards from a marine substrate. that is also assuming that equilibrium is as some say it is.

I do know that there are critters that move though the sand bed quite easily. There are worms that have their feeding apparatus pointing down and their arse end and breathing apparatus pointing up in order to take advantage of food in anaerobic zones. The 'crap' does not always just move down.

are you saying that these worms can eat less material than they can poo? how is this worm population going to survive? i bet if you could find these worms, you could make a nice amount of money selling them to those keeping substrates.

As for a noob posting in an advanced thread/forum, ya can't learn to swim if ya don't jump in the deep end. :fun2:

everyone has to start somewhere. the point of forums is to learn and pass ideas between. the length of being a member is not a good metric for intelligence.

Edit: Oh yea, poop. You'd be surprised how well studied critter poop is. They all excrete some form of solid.

+1

IMO our tanks probable compare more closely to a lagoon than the open ocean reefs. If you have some good strong currents and tidal flushing to clean clean out the gunk, you get nice some nice reefs in those lagoons. Lack of strong currents and lack of tidal flushing, and the sediment starts building up. Do your maintenance (tidal flushing) and grow some nice corals or try the no maintenance routine and have a nice marsh full of detrital sediment build up

absolutely.

I've been following this thread for a while, and I would tend to agree with the camp that the diagram of the global phosphorous cycle is a poor analogy for what happens in aquariums. The issue is the scale at which these processes are taking place. While it is true that P is eventually sequestered in deep sea sediments, the sand beds in our tanks cannot and will not ever resemble, under any circumstances, deep sea conditions. There is a drastic change in P concentrations in sea water from the surface to the deep sea, and the processes that sequester P permanently in the deep ocean are as much a function of the different processes occurring at different depths over vast amounts of space and time as they are anything else. Suggesting that a deep sand bed, which at best simulates a few square feet of the top 4-6 inches of substrate of a shallow bay, lagoon, or tidal pool, in a time scale measured at most in decades (but usually much less) operates anything at all like the deep ocean on a time scale measured in millennia, from a physical or biotic point of view, is stretching it by a mile.

i am confused, are you proving my point, or some other point? the same reasons why the P level increases as you go deeper is the same reason why in a substrate the P level also increases. even water has layers and equilibrium can only happen so fast across distances.

again, there is no difference between how a lagoon and the deep see behave compared to the settling of P, or any organic material. the differences come with access to tidal flushing or major disturbing events. these events affect a substrate deeper, than even our "deepest" substrates.

Also, while yes it is true that phosphate can bind directly to the surface of aragonite, this process is not irreversible. Phosphate binds best to aragonite in sea water at a pH of around 8.4. If the aragonite crystals are not growing and trapping the P inside the structure of the mineral itself, the P is free to be liberated either by a drop in pH, or a change in the equilibrium concentrations. I've not read any articles on the pH gradient present within a DSB, but I would hazard a guess that the pH in the anoxic zone is not the same as the display tank at large. It's very possible that the pH within a DSB is not favourable for the adsorption of P to the surface of calcium carbonate, and regardless if you run your tank at a lower pH you can actually quite easily encourage the liberation of P from calcium carbonate or at least make it a non-significant source of P sequestration. It's one of the reasons that Randy Holmes-Farley suggests running tanks at a higher pH or dosing with limewater as it discourages the release of P from rocks and sand that is possible at a lower pH

you would be correct if we only had to worry about chemistry in our systems. bacteria are the biggest consumer of P in our systems. it is they that are pulling the P off of the calcium carbonate and not the pH or the equilibrium. it is the bacteria that are driving the P cycle and it is them that we rely on for providing P for other organisms in our system. if P were not doing this, then life on Earth would not exist. the bacteria are driving the equilibrium reaction towards the substrate and not away.

Further, if the aragonite crystal is indeed growing, which is possible under a variety of circumstances present in home aquariums, the aragonite does in fact have an inexhaustible capacity to bind and sequester P. As the crystal grows, P gets incorporated right in to the crystal structure, and more binding sites for P are created.

think about the bacteria. this is why the bacteria are driving the equilibrium reaction towards the substrate and not into the water column. the bacteria are creating new binding sites on the aragonite. throwing the equilibrium action towards the aragonite.

So while yes, the P in a DSB does not get easily converted to gas like nitrogen does, it does not mean that it's always trapped there forever. Assuming the bed is working as it should, and that all solid waste is broken down to the point where it's soluble again, it will either get taken up by something else, or eventually exported from the system by the skimmer or some sort of phosphate binding media.

if it gets taken up by something else, then that something else will poo it back out. isn't that the whole point of keeping the ecosystem? to always feed something else? a growing population of any organism is proof of a growing supply of food. the entire ecosystem is powered by the ability of bacteria to access P from inorganic sources. a bed "working" like is should is just binding more P. that is how beds work. it is only those in the aquarium hobby that think otherwise.

Saying that calcium carbonate (be that rocks or sand) is permanent sink for P that eventually "fills up" in any aquarium ignores the more nuanced relationship between the different forms of orthophosphate and their propensity to be adsorbed, pH, and relative concentrations. There are conditions where it is true, but there are lots of other conditions where it is not.

stop thinking chemically, think bacterial. our systems are bacterial driven. they need to be. we use the bacteria for everything. we need to understand what they are doing in order to get a better understanding of what is going on in our systems. looking at the chemistry is only going to give us a partial picture of what is going on in our systems. the nitrate cycle is not chemistry, but bacterial. ammonia is not just going to be converted to nitrate because. the bacteria do it. what do the bacteria need to do this?

G~

 

[asylumdown]

i am confused, are you proving my point, or some other point? the same reasons why the P level increases as you go deeper is the same reason why in a substrate the P level also increases. even water has layers and equilibrium can only happen so fast across distances.

again, there is no difference between how a lagoon and the deep see behave compared to the settling of P, or any organic material. the differences come with access to tidal flushing or major disturbing events. these events affect a substrate deeper, than even our "deepest" substrates.

No, the reason P decreases as you go deeper is because there's nothing photosynthesizing to take it up. The closer you get to the surface, the more light, the more dissolved P gets immediately consumed by living organisms. A coral reef has low dissolved nutrients because it's the most efficient ecosystem on earth, not because the compounds aren't present. It's not about diffusion gradients. By mass, there's mountains of P and N on a coral reef, you just don't find it in the water column. That's the whole point of a deep sand bed - recycle the inputs as much as is conceivably possible while providing as many opportunities for the export of any ions or molecules that are not otherwise being used as possible. Nitrogen eventually gets off-gassed, and phosphate gets recycled until it ends up getting skimmed out in organic matter, bound to a phosphate absorbing resin, incorporated in to the tissue of corals, or locked up forever in the crystal matrix of aragonite. In some cases that might mean a long term net accumulation of P in the system, in some cases it might not, and even if it does, that does not necessarily mean that from a coral keeping point of view you will ever have a problem so long as the accumulated P is in desirable tank biomass and not in the water column or problem algae. It depends on the system and how it's set up. It may be the case that P accumulates until it reaches equilibrium with the exports, it may be the case that it doesn't. It's system dependent, which is why you can't make universal statements about deep sand beds being an eternal sink of P.

And yes, there is a drastic difference between a deep sand bed, the sand at the bottom of a lagoon, and muck at the bottom of a deep ocean trench, and further there's even differences within those specific substrates depending on the time scale you are considering. The graph you keep referencing is a hyper simplified chart describing a global process that is measured in terms of eons. Scale is critical when talking about earth system processes. A couple quotes from the geography literature because they say it way better than me:

"œas the dimensions of time and space change, cause-effect relationships may be obscured or even reversed, and the system itself may be described differently" (Schumm and Lichty, 1965 from Time, space, and causality in geomorphology. in the American Journal of Science)

and

"œmany earth-surface systems are inherently dynamically unstable and deterministically chaotic. This indicates that fundamental system-level behaviors vary with scale or resolution, dictating different approaches." (Phillip, 1999 from Methodology, scale, and the field of dreams in Annals of the Association of American Geographers)

The model you are using does not describe things that happen on a micro scale, which is what our tanks are relative to the system you're comparing them to. The processes that result in the deep sea bed being a net sink of P as measured in geologic time are not good analogies for an aquarium. At the micro scale, there is far more exchange of phosphate in a high energy, biologically active system than the diagram you reference can account for. There are no zones in aquariums that replicate kilometres of cold, pitch black water with little to no life of any kind that decomposing material can sink through. The sand beds people keep in their tanks have an order of magnitude more biological activity in them than an equivalent volume of sediment in a frigid deep ocean sea bed that relies 100% on falling material for energy. The chemistry in our aquariums is significantly different from the ocean, in which many of the ions are never in equilibrium driving permanent precipitation reactions. calcium and carbonate are not in equilibrium in the ocean, and in the deep ocean the equilibrium states of phosphate and calcium are far more favourable for the spontaneous precipitation of calcium phosphate minerals, which in geologic time eventually get sequestered because they get buried by material from above. It's true that on the sea bed there might be some exchange and recycling of P when you look at it on the micro scale, but on a macro scale at that depth the net effect, across millions of years, is a sink. That is nothing like a deep sand bed, where our 'net' effects are measured in terms of months and years and are subject to totally different physical, biotic, and chemical conditions.

you would be correct if we only had to worry about chemistry in our systems. bacteria are the biggest consumer of P in our systems. it is they that are pulling the P off of the calcium carbonate and not the pH or the equilibrium. it is the bacteria that are driving the P cycle and it is them that we rely on for providing P for other organisms in our system. if P were not doing this, then life on Earth would not exist. the bacteria are driving the equilibrium reaction towards the substrate and not away.

think about the bacteria. this is why the bacteria are driving the equilibrium reaction towards the substrate and not into the water column. the bacteria are creating new binding sites on the aragonite. throwing the equilibrium action towards the aragonite.

You are confusing bacterial metabolism with a chemical reaction. The bacteria do not 'create new binding sites'. If they are scavenging phosphate that has been bound to aragonite, all they're doing is opening up an existing binding site, not creating a new one. Once that Phosphate is inside the tissue of the bacteria it is a) now bound up in organic molecules that can eventually be skimmed out or consumed by corals (which you want) and b) no longer an inorganic nutrient that can diffuse back in to the water column, which you also want. Further, to say you know for sure that bacteria scavenging phosphate that is bound to aragonite crystals is a significant component of the micro-scale phosphate cycle in aquarium really should be backed up with some sort of a reference. There's plenty of forms of organic and inorganic phosphate, and they're in constant transition from one state to another with differing levels of bioavailability to different kinds of organisms, both on land and in the sea, how do you know for certain that that specific bacterial pathway for that form of orthophosphate is possible, significant, or favoured?

if it gets taken up by something else, then that something else will poo it back out. isn't that the whole point of keeping the ecosystem? to always feed something else? a growing population of any organism is proof of a growing supply of food. the entire ecosystem is powered by the ability of bacteria to access P from inorganic sources. a bed "working" like is should is just binding more P. that is how beds work. it is only those in the aquarium hobby that think otherwise.

Yes exactly. It gets pooped out. That's why we have skimmers. You can have lots of life in a tank, fed by a complex food web that keeps inorganic nutrients locked up in the tissues of living things for the entire time that it's in your system and still have something that resembles a 'low nutrient' system, because the nutrients aren't in the water. That's the point. Having bacteria take up inorganic phosphate means that at some point, it will either be eaten by things you are trying to grow, or get permanently exported by a skimmer.

stop thinking chemically, think bacterial. our systems are bacterial driven. they need to be. we use the bacteria for everything. we need to understand what they are doing in order to get a better understanding of what is going on in our systems. looking at the chemistry is only going to give us a partial picture of what is going on in our systems. the nitrate cycle is not chemistry, but bacterial. ammonia is not just going to be converted to nitrate because. the bacteria do it. what do the bacteria need to do this?

G~

On this last point I completely agree with you, where I disagree is that that a priori means that a DSB is by default going to result in a perpetual accumulation of problematic P. There are too many biotic and chemical ways for the inorganic P that winds up in a sand bed to either become liberated as soluble inorganic P and removed by phosphate binding media, get permanently sequestered in the tank itself (as in the case of growing aragonite crystals), or consumed and turned in to organic P and either eventually get skimmed out, or removed through trimming of macro algae. I am not saying that it can't become a problem, and the possibility of things going wrong that I can't see and have no control over is one of the reasons why I've never run a DSB, but what I am saying is that a blanket statement about the nature of DSBs made based on an analogy to a process that operates on a completely different spatial and temporal scale is not appropriate, and does not assist in understanding what's going on in your tank.

Having no sand bed and vacuuming up detritus also works, it just works on a different principle. You'll note that November's TOTM on RC, which is spectacular, has a DSB and has been running it for 2 or 3 years. Lots of ways to skin a cat.

 

[asylumdown]

and just a final thought - it would be equally inappropriate for me to conclude that my sand bed is a net sink of inorganic C based on a diagram of the global carbon cycle. Scale matters.

 

[nmbeg]

Are there real examples of conical systems out there?

 

[Reefin' Dude]

No, the reason P decreases as you go deeper is because there's nothing photosynthesizing to take it up. The closer you get to the surface, the more light, the more dissolved P gets immediately consumed by living organisms. A coral reef has low dissolved nutrients because it's the most efficient ecosystem on earth, not because the compounds aren't present. It's not about diffusion gradients. By mass, there's mountains of P and N on a coral reef, you just don't find it in the water column. That's the whole point of a deep sand bed - recycle the inputs as much as is conceivably possible while providing as many opportunities for the export of any ions or molecules that are not otherwise being used as possible. Nitrogen eventually gets off-gassed, and phosphate gets recycled until it ends up getting skimmed out in organic matter, bound to a phosphate absorbing resin, incorporated in to the tissue of corals, or locked up forever in the crystal matrix of aragonite. In some cases that might mean a long term net accumulation of P in the system, in some cases it might not, and even if it does, that does not necessarily mean that from a coral keeping point of view you will ever have a problem so long as the accumulated P is in desirable tank biomass and not in the water column or problem algae. It depends on the system and how it's set up. It may be the case that P accumulates until it reaches equilibrium with the exports, it may be the case that it doesn't. It's system dependent, which is why you can't make universal statements about deep sand beds being an eternal sink of P.

again, i am not sure which point you are trying to prove. you are missing the point here. P is P, it doesn't matter whether it is inorganic or organic, it is still there. all we can test for is inorganic P. if the test results is all we are using to see what the total P is in our systems, then we are missing the vast majority of P because it is used/converted by all of the living organisms in the system. this s what i am trying to get at. stop using P tests, unless they have a margin of error less than 0.001ppm, and start using the biomass. the more biomass the more P in the system. it is as simple as that. it doesn't matter what a test kit says, if there is a lot of biomass in the system, then there is a lot of P in the system, you can not have one without the other.

stop thinking that P is locked, it is not. it is in constant motion. it is used for energy by living organisms. it is converted from one form to another constantly. it does not stay still. you want to think that once it is in an organism or on aragonite it is there for good. this is far from the true. life on Earth would stop if this were true. think of P like you would think of H20, it is constantly in motion. it goes through organisms constantly it does not stay still. we drink water, some stays inside us for a bit, but eventually it gets sweated out or expelled through other methods. it does not sit still. i think you need to look at ATP and ADP reactions to get a clearer picture of what P does.

And yes, there is a drastic difference between a deep sand bed, the sand at the bottom of a lagoon, and muck at the bottom of a deep ocean trench, and further there's even differences within those specific substrates depending on the time scale you are considering. The graph you keep referencing is a hyper simplified chart describing a global process that is measured in terms of eons. Scale is critical when talking about earth system processes. A couple quotes from the geography literature because they say it way better than me:

"œas the dimensions of time and space change, cause-effect relationships may be obscured or even reversed, and the system itself may be described differently" (Schumm and Lichty, 1965 from Time, space, and causality in geomorphology. in the American Journal of Science)

and

"œmany earth-surface systems are inherently dynamically unstable and deterministically chaotic. This indicates that fundamental system-level behaviors vary with scale or resolution, dictating different approaches." (Phillip, 1999 from Methodology, scale, and the field of dreams in Annals of the Association of American Geographers)

go ahead find me a P chart that works on the scale you want. nobody is stoping you. are you saying that rabbits work on the geological scale? the first chart is simplified, but it shows the primary directions of P, whether it is macro, or micro. they are both in that graph or the second one i posted. if you really want to look at P under the microscope, then look up ATP, ADP, and the Calvin cycle. be careful though, following the P trail will lead to all kinds of rabbit holes of information.

The model you are using does not describe things that happen on a micro scale, which is what our tanks are relative to the system you're comparing them to. The processes that result in the deep sea bed being a net sink of P as measured in geologic time are not good analogies for an aquarium. At the micro scale, there is far more exchange of phosphate in a high energy, biologically active system than the diagram you reference can account for. There are no zones in aquariums that replicate kilometres of cold, pitch black water with little to no life of any kind that decomposing material can sink through. The sand beds people keep in their tanks have an order of magnitude more biological activity in them than an equivalent volume of sediment in a frigid deep ocean sea bed that relies 100% on falling material for energy. The chemistry in our aquariums is significantly different from the ocean, in which many of the ions are never in equilibrium driving permanent precipitation reactions. calcium and carbonate are not in equilibrium in the ocean, and in the deep ocean the equilibrium states of phosphate and calcium are far more favourable for the spontaneous precipitation of calcium phosphate minerals, which in geologic time eventually get sequestered because they get buried by material from above. It's true that on the sea bed there might be some exchange and recycling of P when you look at it on the micro scale, but on a macro scale at that depth the net effect, across millions of years, is a sink. That is nothing like a deep sand bed, where our 'net' effects are measured in terms of months and years and are subject to totally different physical, biotic, and chemical conditions.

how are they different? feel free to post references on how our systems are different than what is going on in nature, whether micro or macro. how do our systems, defy the law of gravity for settling of material, or how the organisms in our systems take in less food, than they produce in waste. that is what you are saying. if the organisms in the substrate made P and N go away, then what would the organisms live on? how could there be an ecosystem if all of the organisms used up more N and P than they take in? the conservation of mass does not work that way.

You are confusing bacterial metabolism with a chemical reaction. The bacteria do not 'create new binding sites'. If they are scavenging phosphate that has been bound to aragonite, all they're doing is opening up an existing binding site, not creating a new one. Once that Phosphate is inside the tissue of the bacteria it is a) now bound up in organic molecules that can eventually be skimmed out or consumed by corals (which you want) and b) no longer an inorganic nutrient that can diffuse back in to the water column, which you also want. Further, to say you know for sure that bacteria scavenging phosphate that is bound to aragonite crystals is a significant component of the micro-scale phosphate cycle in aquarium really should be backed up with some sort of a reference. There's plenty of forms of organic and inorganic phosphate, and they're in constant transition from one state to another with differing levels of bioavailability to different kinds of organisms, both on land and in the sea, how do you know for certain that that specific bacterial pathway for that form of orthophosphate is possible, significant, or favoured?

i think you are the one that is confusing the binding sites. you are correct, bacteria are not opening up completely new sites, they are opening up sites that were previously closed because they were filled with P.

Phosphate solubilizing bacteria

again, life on Earth depends on these bacteria. without these bacteria P would never be able to get back into the ecosystem for an organism to use again. it is these bacteria that actually allow plant roots to uptake P. plants are not able to do uptake P without these bacteria first liberating the P from the inorganic source and getting it into solution for the roots.

what other references would you like for this process?

Phosphorus Uptake by Plants: From Soil to Cell

Variable rates of phosphate uptake by shallow marine . carbonate sediments:
Mechanisms and ecological significance

Uptake of phosphate ions by calcium carbonate

Yes exactly. It gets pooped out. That's why we have skimmers. You can have lots of life in a tank, fed by a complex food web that keeps inorganic nutrients locked up in the tissues of living things for the entire time that it's in your system and still have something that resembles a 'low nutrient' system, because the nutrients aren't in the water. That's the point. Having bacteria take up inorganic phosphate means that at some point, it will either be eaten by things you are trying to grow, or get permanently exported by a skimmer.

the skimmer can only get the waste products that are available floating in the water column. the organisms in the substrate are not doing this. they are producing their wastes in the substrate, the skimmer does not have access to these. if it did, then the next stage in the Harry Potter substrate ecosystem would not have anything to eat to feed the next chain in the ecosystem.

we are looking at total P, not just inorganic P. it doesn't matter whether it is temporarily locked up in an organism or stuck to aragonite. it is still in the system and is on the move. it will get used by another organism sooner rather than later. the less biomass you see, the less total P there is in the system. depending on the trophic level one wants to maintain will determine how much extra biomass is wanted or necessary.

On this last point I completely agree with you, where I disagree is that that a priori means that a DSB is by default going to result in a perpetual accumulation of problematic P. There are too many biotic and chemical ways for the inorganic P that winds up in a sand bed to either become liberated as soluble inorganic P and removed by phosphate binding media, get permanently sequestered in the tank itself (as in the case of growing aragonite crystals), or consumed and turned in to organic P and either eventually get skimmed out, or removed through trimming of macro algae. I am not saying that it can't become a problem, and the possibility of things going wrong that I can't see and have no control over is one of the reasons why I've never run a DSB, but what I am saying is that a blanket statement about the nature of DSBs made based on an analogy to a process that operates on a completely different spatial and temporal scale is not appropriate, and does not assist in understanding what's going on in your tank.

the greater the access to the main water column for the detritus, the more likely the system will act like you are suggesting. with a BB system being on the immediately available side of things to a DSB being on the other. with the BB behaving most like what you want. any decomposition or utilization by other organisms leads to a more direct path to the skimmer. there is nowhere for the nutrients to hide. the more material in the way, the less the processes are going to work the way you want them to.

Having no sand bed and vacuuming up detritus also works, it just works on a different principle. You'll note that November's TOTM on RC, which is spectacular, has a DSB and has been running it for 2 or 3 years. Lots of ways to skin a cat.

i thought we went through how DSB's work. it is the slow migration of nutrients downward through a substrate leaving the upper levels able to bring in more nutrients from the water column. this is how DSB's work, and this is why they "seem" to work so well. they are a limited maintenance P sink while they are functioning properly. they can temporarily bind a huge amount of nutrients, but unfortunately they will not be able to uptake enough nutrients to maintain the wanted trophic level. in other words equalization has reached the upper levels of the substrate meaning more and more nutrients are available in the main water column. the more reliance needed on P removers, carbon sources, or a larger P sink (also known as live sumps, ATS's, RDSB's).

the point is that the cat still needs to be skinned. with skinning being the removal of P, and not just hiding it in an ecosystem. this means that the TOTAL amount of P should be able to be maintained. total being both testable inorganic P and P contained in those organisms wanted, unwanted, or supporting. we should only be keeping the amount of nutrients needed for the organisms we WANT to keep thriving.

G~

 

[Mg4life0331]

FWIW, I am going to run a DSB in my small refuge. Im then going to culture what ever bacteria I can and come back with results. I had another thread on this and Im joining the party late on this one.

 

[Reefin' Dude]

Are there real examples of conical systems out there?

there are a few examples out there. the biggest problems people are having with them is that detritus seems to "stick" to the HDPE a bit more than we thought. most just smack the tank with a rubber mallet to break it loose and let it fall down before turning the valve to remove the detritus.

those that have them, love them. super quick water changes. removes the detritus without needed to go into the water column at all, or very seldom.

G~

 

[onetrickpony]

substrate can be used to great affect in this manner for a while. a skimmer is not going to get it all, and in fact if the calcium carbonate bacterial tug of war did not exist our systems would not be alive. skimmers are fantastic exporters of organic P. i think they need to be bigger though. i am also a big fan of settling tanks, think empty live sumps. a place to see and easily remove accumulating detritus. conical setting tanks being better because of the nice valve on the bottom.

there is always going to be an increase in P in an undisturbed substrate even with the biggest skimmers or the most flow. it is the calcium carbonates ability to bind with inorganic P that makes the whole shebang seem to work. those that use substrates are relying on this interaction. it is the substrate that is keeping the N and P levels the way they are as long as they are without significant disruption of the substrate to clean it out.

From reading all this, to me it all comes down to nutrient export and or binding nutrients in biomass.

There are different ways to get this done, sand beds, carbon dosing, protein skimmers, biomass , algae scrubbers, binding agents.

The thing with sand beds is how do you know when its time to change it out.

You cant keep adding to a closed system with out it overflowing at some point.

 

[GroktheCube]

From reading all this, to me it all comes down to nutrient export and or binding nutrients in biomass.

There are different ways to get this done, sand beds, carbon dosing, protein skimmers, biomass , algae scrubbers, binding agents.

The thing with sand beds is how do you know when its time to change it out.

You cant keep adding to a closed system with out it overflowing at some point.

Indeed. The issue with relying solely upon binding in biomass is that no biological process is 100% efficient, there will always be waste. While having more biodiversity with more trophic levels represented increases the efficiency at which the tank as a whole will utilize input, there will ALWAYS be waste that needs to be disposed of.

I just vaccumed my sandbed for the first time in a few months, and it was very satisfying! I turned an entire 5 micron sock dark, dark brown, and my sand "appears" very clean to the naked eye. Lately I've needed to run GFO to keep phosphates low enough, so I figured it was time.

While systems like DSBs snd refugia may do a pretty good job recycling nutrient input, they certainly can't do it with 100% efficiency, and thus cannot be truly maintenance free.

 

[dppitone]

I use deep sand beds because I enjoy the life support. There are loads of tubeworms and amphipods poking out and crawling over the sand beds of our tanks. Thousands of worm tubes are visible in the mornings. The tracks and tunnels all over them and seen through the glass under the surface are really cool. I've had the DSBs for about 20 years. I've never touched them, done maintenance on them, etc. I've never changed them out - and in fact when someone offers live sand I always grab it and add it to the beds we have, importing more life and diversity.

I think of the sand bad as an additional integrated habitat that adds up to our more natural reef environ.

If I hadn't happened across posts that said DSBs can/are dangerous, I would have never known. I don't know of any problem I've had that can be contributed to them. It doesn't mean that they're not dangerous, I don't know, I've just never had an concern that I'm aware of. I tend to believe that folks over-think this matter.

Dave

 

[Bilk]

From reading all this, to me it all comes down to nutrient export and or binding nutrients in biomass.

There are different ways to get this done, sand beds, carbon dosing, protein skimmers, biomass , algae scrubbers, binding agents.

The thing with sand beds is how do you know when its time to change it out.

You cant keep adding to a closed system with out it overflowing at some point.

The argument against DSB has always had a flaw, that no other means of export are being employed by the user of a DSB. That would be like claiming someone who uses a filter sock doesn't utilize other means of export or can create problems in their system if they don't service the sock. Most everyone with success uses more than one method of filtration, and in many cases quite a few. A DSB is just one component in a filtration system.

 

[Bilk]

I'd like to postulate that overflows are more an issue regarding accumulation of nutrients than DSB for many hobbyists, and especially so if they're internal. I suspect they are the least maintained component of many systems; a place where everything we want to export from our systems, must flow.

Internal skimmers are for the most part, used by those who will place their tank against a wall, which then severely limits the access to the overflow for cleaning and removing detrital buildup and algae that trap detritus. Further complicating the situation, is the fact that the majority of internal overflows are as deep as the tank - not all, but most all reef ready tanks.

So with limited access and no ability to visually see what's occurring in the overflow, I suspect that most do not provide maintenance for this extremely important interface between the body of water we're attempting to maintain and the filtration system/media in the sump. So therefor by extension we can make the claim that overflows, and particularly internal overflows, are dangerous in a marine aquariums :eek2:

So the next time we read a post where someone is claiming to have issues with pests but they run this that and the other thing, clean their filter socks religiously and have super lights with the latest, greatest skimmer and run UV and ozone, the first thing we should ask is - when's the last time you cleaned your overflow?

 

[GroktheCube]

I'd like to postulate that overflows are more an issue regarding accumulation of nutrients than DSB for many hobbyists, and especially so if they're internal. I suspect they are the least maintained component of many systems; a place where everything we want to export from our systems, must flow.

Internal skimmers are for the most part, used by those who will place their tank against a wall, which then severely limits the access to the overflow for cleaning and removing detrital buildup and algae that trap detritus. Further complicating the situation, is the fact that the majority of internal overflows are as deep as the tank - not all, but most all reef ready tanks.

So with limited access and no ability to visually see what's occurring in the overflow, I suspect that most do not provide maintenance for this extremely important interface between the body of water we're attempting to maintain and the filtration system/media in the sump. So therefor by extension we can make the claim that overflows, and particularly internal overflows, are dangerous in a marine aquariums :eek2:

So the next time we read a post where someone is claiming to have issues with pests but they run this that and the other thing, clean their filter socks religiously and have super lights with the latest, greatest skimmer and run UV and ozone, the first thing we should ask is - when's the last time you cleaned your overflow?

Heh, my overflow box is a bit of a disaster, actually!

I've got my in tank aiptasia problem reasonably well controlled at this point, fingers crossed there won't be any more visible within a month or so at the rate I'm going, but by overflow box is FILLED with the little buggers. I'm not quite sure how to get them out either!

I'm considering just draining it and allowing it to dry for a few hours.

Maybe not quite the same danger as a mountain of detritus, but I can't even imagine the damage they could do to my aiptasia elimination regimen if they all released planula at once .

 

[Bilk]

Heh, my overflow box is a bit of a disaster, actually!

I've got my in tank aiptasia problem reasonably well controlled at this point, fingers crossed there won't be any more visible within a month or so at the rate I'm going, but by overflow box is FILLED with the little buggers. I'm not quite sure how to get them out either!

I'm considering just draining it and allowing it to dry for a few hours.

Maybe not quite the same danger as a mountain of detritus, but I can't even imagine the damage they could do to my aiptasia elimination regimen if they all released planula at once .

Well they're in there for the good eats You could probably nuke the overflow with saturated kalkwasser after it's drained and sealed off from everything. Then a few good rinsings and you're good to go.

As for the tank denizens, I had pretty good success with berghia nudibranchs. I had maybe 6 or seven visible nasties, but if there were that many visible, I figured there were more, so I gave the nudie a try and those I was able to see are gone. I won't hesitate to use them again when the need arrises. If, if. I said if!

 

[billsreef]

Heh, my overflow box is a bit of a disaster, actually!

I've got my in tank aiptasia problem reasonably well controlled at this point, fingers crossed there won't be any more visible within a month or so at the rate I'm going, but by overflow box is FILLED with the little buggers. I'm not quite sure how to get them out either!

I'm considering just draining it and allowing it to dry for a few hours.

Maybe not quite the same danger as a mountain of detritus, but I can't even imagine the damage they could do to my aiptasia elimination regimen if they all released planula at once .

It's going to take a lot more than a few hours drying Those buggers are quite resilient, you'll need to make them bone dry. Probably be easier to plug the overflow, drain it and then refill it with pure fresh water for several hours, maybe even straight up hydrogen peroxide since your going for the kill. Either way should nuke them, and without using any chemicals that will leave problematic residuals.

 

[dppitone]

perhaps just surrender

 

[Bilk]

It's going to take a lot more than a few hours drying Those buggers are quite resilient, you'll need to make them bone dry. Probably be easier to plug the overflow, drain it and then refill it with pure fresh water for several hours, maybe even straight up hydrogen peroxide since your going for the kill. Either way should nuke them, and without using any chemicals that will leave problematic residuals.

Yeah they are practically indestructible. I had some rock with aiptasia sitting in a container of saltwater for a few weeks with no heating, water movement or filtration. The temp dropped significantly and the salinity had to nearly double from evaporation of a good portion the water There must have been a pretty good ammonia spike too. Those buggers were still alive. Not happy, but alive.

The overflow can easily be isolated for nuking purposes :uzi: :smokin: