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

[Randy Holmes-Farley]

what makes a substrate work is the slow migration of P downward

Why not upward and out to the water column?

 

[billsreef]

there are a few "sand experts" i can think of that made the claim that one should not touch a substrate once it has been setup, let the critters do the work.

I'd debate calling them "sand experts"

BTW, don't forget, of all the P being dumped into the tank in the form of food, a percentage of it is bound up in the organisms eating the food, and more is bound up the organisms eating the waste of the critters eating the food Hence, you don't need to remove P at quite the same rate as it's put in, but rather the rate of the excess to the systems needs. So, yup, we still need intervention to export P (and other extras) to prevent the system from becoming a swamp instead of a reef.

 

[billsreef]

what makes a substrate work is the slow migration of P downward

Why not upward and out to the water column?

And thence to be bound up in algal growth, removed via protein skimming, GFO, and water changes

 

[Fredfish]

So are we agreed then on where nutrients come from in a newly set up tank and where they would come from in a mature tank/sand bed?

As to sand experts that recommended not disturbing the sand, the three that I am aware of are Robert Toonan, Ron Schemic and Eric Borneman, all being marine biologists. I don't know what 'experts' you had in mind.

The primary reason for this is that you do not want to disturb the invertibrate habitat that has been established. This does happen all the time in the ocean, but you have a much larger ecosystem from which to repopulate a disturbed sand bed.

In an aquarium you risk destroying a significant portion of your invertibrate population if you are always stirring and syphoning.

BTW, don't forget, of all the P being dumped into the tank in the form of food, a percentage of it is bound up in the organisms eating the food, and more is bound up the organisms eating the waste of the critters eating the food Hence, you don't need to remove P at quite the same rate as it's put in, but rather the rate of the excess to the systems needs. So, yup, we still need intervention to export P (and other extras) to prevent the system from becoming a swamp instead of a reef.

What I find interesting is the range of experience on the rate nutrient build up. We have had a few people here that have had sand beds in the range of 7-10 years without doing any syphoning.

Unfortunately there is no set formula for success. Knowing this, I would not put a deep sand bed in my display tank, but would keep in in a refugium where it is easier to deal with if things do not go well.

 

[tmz]

N is not as big of a concern as P.

Why?Amoninia toxicity and stress to some corals from excessive NO3 for exampleon the down side vs alteration in the calcification process with higher phosphate . On the other hand both fixed nitrogen and phosphate are needed by living things. I think they go hand in hand .Phosphate reduction will not happen if the organisms taking it up don't have adequate nitrogen for example. They are both potential somewhat interdependent concerns, IMO.

 

[tmz]

there must be an organism that is producing more material as waste, then it is taking in. it just doesn't work that way.
Organisms use reactive phosphate for in their structures and ATP /ADP and other needs. Inorganic and some organic phosphate may be used .As these organisms are exported or the organic compounds they produce are ,phosphate goes with them.
Some organic compounds are refractory (don't breakdown) ;some phosphate is likely sunk in some of those.
Some phosphate will bind to calcium carbonate surfaces and may return as equilibartion with the srrounding water occurs.
Some will penetrate the calcium carbonate crystal matrix and be sunk there or in bone and skeletal mass unlikely to dissolve in a typical reef tank. Phosphate is also mineralized and sunk as apatite and phosphorite and in other forms. As such reactive phosphate is reduced without tinkerbell. intervening.

These ideas are not new ;they also happen to be in the 15 to 25 year old papers linked earlier.The ocean does a fine job of maintaining consistent levels in the water in balnce with inputs from a varity of sources 'perhaps mostly esturaial runoff, and even maintains large sinks of phosphorite reserves from long long ageo

I don't think extrapolations from ocean studies are easily made for reef tanks and have not seen any data to support the notion that phosphate sinks in reef aquaria are dangerous. They are not so in the sea obviously. I don't think, the upwelling on reefs from deep waters and sediments is really the same(pressure temp pH etc) as the activit in several inches of sand

 

[tmz]

Unfortunately there is no set formula for success. Knowing this, I would not put a deep sand bed in my display tank, but would keep in in a refugium where it is easier to deal with if things do not go well.

I'd put one in a tank if I had animals that needed it and wouldn't hesitate if I wanted to keep certain specimens . There really isn't a reason to fear deep sand. There is a need to maintain it.
After having deep beds for a long time ,I'm not personally pleased with the aesthetics but do use puddles of deep sand for burrowing wrasses and tube anemones.

In a refugium, I think shallow sand over a larger footprint might improve the dentirification without a make or break reliance on sand critters for nutrient (C,N and Pi) transport deep but that's just my thinking. Some structure on top form live rock or something else can also enhance advective flow into the bed but is probably not enough to make a big difference in delivering enough nutrients to keep denitrifying bacteria chugging along at good speed.
I'm sure there are many ways to mange the substrate successfully to suit one's preference and enjoyment.

 

[Fredfish]

I'd put one in a tank if I had animals that needed it and wouldn't hesitate if I wanted to keep certain specimens . There really isn't a reason to fear deep sand. There is a need to maintain it.

I would certainly use one for animals that need it. It's not so much fear as ease of mainenance if required. I'm much more likely to do something if its easy to do.

 

[Reefin' Dude]

what makes a substrate work is the slow migration of P downward

Why not upward and out to the water column?

1) because land life wouldn't exist. if P did not get locked up in substrates, then there would not be a mechanism for P to become available for land based organisms, it would all become locked up at the substrate water interface. look at any phosphate cycle. they all have P being locked up in marine substrates, then exported by terrestrial upheavals.

2) what would the benthic organisms eat? if all of the P is at the top of the substrate, then what would the organism deep in the substrate eat? they need resources also.

3) how many P compounds are lighter than water in our systems? gravity doesn't work that way.

4) we know P binds to calcium carbonate. how can it bind to calcium carbonate and still work its way upwards? how can it bind and not get locked into the substrate?

5) stir up any substrate that has been setup for any length of time. there is organic material in it, that was not there before. if P migrates upwards, then how did this material get there?

i posted several papers on phosphate sinking in marine substrates, but here is the link to that post. post 316.

G~

 

[Reefin' Dude]

I'd debate calling them "sand experts"

BTW, don't forget, of all the P being dumped into the tank in the form of food, a percentage of it is bound up in the organisms eating the food, and more is bound up the organisms eating the waste of the critters eating the food Hence, you don't need to remove P at quite the same rate as it's put in, but rather the rate of the excess to the systems needs. So, yup, we still need intervention to export P (and other extras) to prevent the system from becoming a swamp instead of a reef.

lets start with you eating 4 big macs. each being a 1/4 each. how much of that total mass becomes bound into you? are you still growing? if you keep eating 4 big macs every meal you would be, but not in a healthy way. for you to maintain you mass you must expel an equal amount of mass. this goes for all organisms. the vast majority of material coming in goes right out as waste.

And thence to be bound up in algal growth, removed via protein skimming, GFO, and water changes

where is the inorganic P coming from that GFO and the bacteria removed by skimming comes from? take a step back and think through the entire P cycle. using GFO, algae, carbon dosing is like using the fan in the rest room to remove the stink instead of just flushing the toilet. the inorganic P has to come from somewhere, where?

So are we agreed then on where nutrients come from in a newly set up tank and where they would come from in a mature tank/sand bed?

probably not. depends on how the tank was setup, but i would say most of the P in a newly setup tank comes from the calcium carbonate structures. most of the calcium carbonate structures we get are land based. land based calcium carbonate is high in phosphates. look up phosphates mining. unless P is not locked up in marine substrates.

As to sand experts that recommended not disturbing the sand, the three that I am aware of are Robert Toonan, Ron Schemic and Eric Borneman, all being marine biologists. I don't know what 'experts' you had in mind.

yep, those will do. how many marine substrates do you know of in nature that are not disturbed? how many of those are in oligotrophic environments? when a tropical storm comes through an area, do you believe that the marine substrates in that area are not significantly disturbed? why are we not emulating nature and disrupting the substrates on a regular basis to clear it out of built up organic material. we are so fixated on how nature works, but we are ignoring a major process that goes on in all tropical areas.

The primary reason for this is that you do not want to disturb the invertibrate habitat that has been established. This does happen all the time in the ocean, but you have a much larger ecosystem from which to repopulate a disturbed sand bed.

but wait, if P migrates upwards, then what do these benthic organisms eat? there would not be any P in the substrate. these habitats are constantly being disturbed in nature. even the simple tides moves more substrate an hour than most of our substrates are deep. this of course is not taking into account tropical storms. repopulate. i hear this a lot. what needs to be repopulated? there is not a magic worm that transports P to the detrital dimension, and it needs to be replaced because on occasion it messes up and transports itself. this is where the sand experts have it all wrong. P is not migrated upwards. it is migrated downwards. if it didn't then land life would not exist. all of the P since the beginning of life on earth would have already been washed down into the oceans. none would become available again for land based organisms.

In an aquarium you risk destroying a significant portion of your invertibrate population if you are always stirring and syphoning.

what is the point of this population? ecosystem and biodiversity are just fancy words for phosphate sinks. they are not doing anything other than increasing the trophic level of the system. what are they feeding on? it goes back to the hamburger example earlier. if bacteria need 4 hamburgers and waste out 3. a pod needs 10 bacteria to live, that means that there must be 40 hamburgers in the system just to support 1 pod. lets say a fish also need 10 pods to live. that means that there are now 400hamburgers in that system to support that fish from the bottom up. why not just feed the fish the 10 pods and not have the added mass of the 400 hamburgers.

What I find interesting is the range of experience on the rate nutrient build up. We have had a few people here that have had sand beds in the range of 7-10 years without doing any syphoning.

this is where it is important to know the trophic level that the individual is wanting to emulate. a minimally disturbed substrate is a great idea for softie and the more eutrophic systems. not so much for oligotrophic systems. another thing to look at is the amount of resources used to cover up the affects of eutrophication. GFO, carbons dosing dohickies, algae, whatever the P remove of choice is this year. these are all covering up the fact that P is no longer being migrated slowly downward through the substrate. the substrate is not pulling in any available inorganic P from the water column. the only way inorganic P is being bound out of the water column is through these P removing resources.

Unfortunately there is no set formula for success. Knowing this, I would not put a deep sand bed in my display tank, but would keep in in a refugium where it is easier to deal with if things do not go well.

sure there is. clean up after your pet. export waste at a rate that maintains the trophic level wishing to be emulated. oligotrophic systems should make waste removal the main priority. eutrophic systems should maintain a higher level of available inorganic nutrients.

N is not as big of a concern as P.

Why?Amoninia toxicity and stress to some corals from excessive NO3 for exampleon the down side vs alteration in the calcification process with higher phosphate . On the other hand both fixed nitrogen and phosphate are needed by living things. I think they go hand in hand .Phosphate reduction will not happen if the organisms taking it up don't have adequate nitrogen for example. They are both potential somewhat interdependent concerns, IMO.

it goes both ways. where is the excess N and P coming from? that is the point here. remove the waste from the organisms so that the oligotrophic organisms remain healthy. it is the breakdown of wastes by bacteria that are disrupting the photosynthesis in hermatypic organisms. the corals need to be in charge, not the zoax. the corals need to be supplying the P and N for the zoax.
we run in to problems when the zoax have access to free N and P from the water column, from the excess waste decomposing in the system. one of the early signs of eutrophication on natural reefs.

there must be an organism that is producing more material as waste, then it is taking in. it just doesn't work that way.
Organisms use reactive phosphate for in their structures and ATP /ADP and other needs. Inorganic and some organic phosphate may be used .As these organisms are exported or the organic compounds they produce are ,phosphate goes with them.
Some organic compounds are refractory (don't breakdown) ;some phosphate is likely sunk in some of those.
Some phosphate will bind to calcium carbonate surfaces and may return as equilibartion with the srrounding water occurs.
Some will penetrate the calcium carbonate crystal matrix and be sunk there or in bone and skeletal mass unlikely to dissolve in a typical reef tank. Phosphate is also mineralized and sunk as apatite and phosphorite and in other forms. As such reactive phosphate is reduced without tinkerbell. intervening.

but none of this would occur if P migrated upwards instead of downwards.

all organisms are P converters. very little of the P that is taken up by an organisms stays in an organisms very long. P is constantly moving. it needs to be in order to provide energy for life.

These ideas are not new ;they also happen to be in the 15 to 25 year old papers linked earlier.The ocean does a fine job of maintaining consistent levels in the water in balnce with inputs from a varity of sources 'perhaps mostly esturaial runoff, and even maintains large sinks of phosphorite reserves from long long ageo

where were these long ago reserves? they were old marine sediments.

I don't think extrapolations from ocean studies are easily made for reef tanks and have not seen any data to support the notion that phosphate sinks in reef aquaria are dangerous. They are not so in the sea obviously. I don't think, the upwelling on reefs from deep waters and sediments is really the same(pressure temp pH etc) as the activit in several inches of sand

why not, we are so fixated on replicating nature. how could we ignore what we are trying to emulate? how does it work in nature, and how do we adapt it to our systems? we have been ignoring how P is sunk or exported from various marine areas. that is our problem. the science is there, we have just been ignoring it because it goes completely against what the sand experts have been saying. they are all about keeping poo as a pet regardless of the trophic state trying to be emulating.

phosphate sinks are not dangerous in our systems or any systems. they just need to be understood and know when they need to be cleaned out. use a DSB if you want. just replace it or clean it on a regular basis to keep it functioning properly.

G~

 

[tmz]

I would certainly use one for animals that need it. It's not so much fear as ease of mainenance if required. I'm much more likely to do something if its easy to do.

I didn't think you were afraid of it ; the thread title drew the reference to fear not your post. I agree maintenance can be an issue to consider in choosing whether or not to have a deep bed in the tank.:hmm5:

 

[asylumdown]

1) because land life wouldn't exist. if P did not get locked up in substrates, then there would not be a mechanism for P to become available for land based organisms, it would all become locked up at the substrate water interface. look at any phosphate cycle. they all have P being locked up in marine substrates, then exported by terrestrial upheavals.

Nothing about that statement makes any sense. Randy was talking about the process of dissolution/diffusion of water soluble forms of phosphorous in to the water column. You seem to be of the impression that chemistry and the physical world has no room for nuance or complexity. On global scales across millions of years, yes, the net effect is for phosphorous in the oceans to become sequestered in deep sediments that eventually form dry bedrock through tectonic uplifting. That's a NET effect of a spatial and temporal process measured in millions of years, kilometres of depth, and millions of square kilometres of area. In the short term, phosphorous actively moves through ALL environments, changing states, degree of availability, exchanging between substrate and solution all the time, every second of the day, everywhere on earth. Phosphorous is the 11th most common element on Earth's crust. It's everywhere. In time scales measured in weeks or months, different molecules containing phosphorous atoms that have different degrees of solubility, are subject to complex equilibrium reactions, and will become either sequestered in a substrate or liberated in to solution depending on a myriad of external factors. The scale that you keep talking about - the million year net sequestration of phosphorous in deep marine sediments operates on a spatial and temporal scale so vastly different from anything that will ever happen in any aquarium, that there is literally no point in talking about it in terms of processes taking place inside an aquarium sand bed. They have nothing to do with each other, involve different processes, different time scales, different substrates, different chemistry, different temperatures, different pressures, and different driving forces. Sand beds and deep ocean sediments aren't even made of the same stuff. Show me a single ROV video of the bottom of the ocean that shows vast fields of aragonite sand - you can't cuz there aren't any. The bottom of the ocean looks more like miracle mud than the sand people put in deep sand beds.

2) what would the benthic organisms eat? if all of the P is at the top of the substrate, then what would the organism deep in the substrate eat? they need resources also.

Randy was talking about Phosphorous dissolving back in to solution, therefore diffusing out in to the water column, not remaining trapped at the top of the substrate. Some orthophosphate is highly water soluble, the rest is partially soluble according external factors affecting it's equilibrium state (factors which can be manipulated by the aquarist by using products such as GFO)

3) how many P compounds are lighter than water in our systems? gravity doesn't work that way.

Gravity has nothing to do with whether or not something is soluble in water. If you mix up a batch of fresh salt water then let it sit in a bucket for a week, the water on the bottom does not become more salty than the water on the top. If you dissolve some form of orthophosphate in to the same bucket of water and let it sit for a week, there will be the same concentration of P in the top 1cm of water as there will be in the bottom 1cm. In an aquarium where the water is being constantly mixed that's going to be even more true. It's why you can take samples of water from your sump to test the concentration of various chemicals in your display.

4) we know P binds to calcium carbonate. how can it bind to calcium carbonate and still work its way upwards? how can it bind and not get locked into the substrate?

Sure does. Calcium carbonate also releases phosphorous under a myriad of different conditions, many of which routinely occur in a normal reef aquarium. Changes in pH and concentration of P in solution can dynamically bind or release P from calcium substrates. You can test this for yourself very easily. Go out and get some marco rock. Put it in some salt water with a known phosphate concentration. Measure that water every day for a while. I promise you, you will find the P levels will increase to a point, then they will stabilize. Now, dose that water with lanthanum chloride (or do a 100% water change), and measure the water again. The levels will probably rise, but probably not as high. You can keep doing this until the rock eventually contributes very little P to the water. It's not a one way process. The relationship between calcium and phosphate is 1000 times more complex and nuanced than you make it out to be.

5) stir up any substrate that has been setup for any length of time. there is organic material in it, that was not there before. if P migrates upwards, then how did this material get there?

Here's where you and I sort of agree. The romantic notion that a deep sand bed magically makes 100% of the organic matter in a system vanish in to gas is 21st century alchemy. Nature is sloppy and always has been, there is no biotic ecosystem process that recycles 100% of the material that moves through it. The only reason planet earth didn't die under it's own septic waste half a billion years ago is because the planet also has a host of abiotic processes working in the background to mop up extra organic matter, oxygen, carbon dioxide, etc. etc, a balance that life has selfishly and self-destructively screwed up multiple times in history. There will always be inert mulm left over, most of which is the unusable (to the things we keep anyway) bacterial waste (i.e., dead biofilms). I would be very interested in a detailed chemical analysis of what's actually in that stuff, and whether or not it interacts with the water chemistry at all. Generally, if something can decompose in to simpler, more available compounds, it will. The fact that that crud collects in the sand, at the bottom of overflows, in sumps, etc. and seems to stay there in that form in perpetuity makes me think it's largely inert, but I don't know if anyone actually knows what that stuff is made of.

i posted several papers on phosphate sinking in marine substrates, but here is the link to that post. post 316.

G~

Good reads for sure, largely irrelevant to the processes taking place in an aquarium. They are not comparable systems.

For the record, I'm not advocating for deep sand beds. I wouldn't personally use one, but more because the theory behind it seems to be based more on a romanticized notion of the natural fallacy that seems to have little connection to what may or may not actually be happening. The deep sand bed methodology makes several specific claims, both about it's effect and it's mode of action. All claims about it's mode of action are based more on what we wish were true than anything that's actually demonstrable, and it fails enough times for enough people to make me think that we actually have no idea what makes them work when they do or fail when they don't.

I'm also not saying I don't think Phosphorous is not a an issue in a reef system given it's propensity to form a bajillion different compounds and bond to calcium. I just don't think that your analogies or examples are a good model to base one's understanding of phosphorous in a marine aquarium off of.

 

[tmz]

Quote:
<table cellpadding="5" cellspacing="0" border="0" width="100%"> <tbody><tr> <td class="alt2" style="border:1px inset"> Originally Posted by tmz
there must be an organism that is producing more material as waste, then it is taking in. it just doesn't work that way.
Organisms use reactive phosphate for in their structures and ATP /ADP and other needs. Inorganic and some organic phosphate may be used .As these organisms are exported or the organic compounds they produce are ,phosphate goes with them.
Some organic compounds are refractory (don't breakdown) ;some phosphate is likely sunk in some of those.
Some phosphate will bind to calcium carbonate surfaces and may return as equilibartion with the srrounding water occurs.
Some will penetrate the calcium carbonate crystal matrix and be sunk there or in bone and skeletal mass unlikely to dissolve in a typical reef tank. Phosphate is also mineralized and sunk as apatite and phosphorite and in other forms. As such reactive phosphate is reduced without tinkerbell. intervening.
</td> </tr> </tbody></table>
but none of this would occur if P migrated upwards instead of downwards.



Upwelling is how nutirents circulate into the food chain . I think you are confusing reactive and mineralized phosphate. I don't think the later will contribute significantly in a reef tank.It's sunk.

 

[Randy Holmes-Farley]

edit: I see others already addressed these points, but I'll leave them here anyway...

because land life wouldn't exist. if P did not get locked up in substrates, then there would not be a mechanism for P to become available for land based organisms, it would all become locked up at the substrate water interface. look at any phosphate cycle. they all have P being locked up in marine substrates, then exported by terrestrial upheavals.

Sorry, I don't have the slightest idea what terrestial upheaval has to do with sand beds releasing posphate back into the water column.

Do you doubt it happens?

Obviously there is phosphate present in marine deposits. That doesn't mean that all or even most of the phosphate that enters the substrate as organic matter ends up in the deposits permanently.

what would the benthic organisms eat? if all of the P is at the top of the substrate, then what would the organism deep in the substrate eat? they need resources also.

Digested organics release inorganic phosphate, and that released ion moves up and down, and some leaves the sand for the water. Noting is starved by that process.

how many P compounds are lighter than water in our systems? gravity doesn't work that way.

Wow, I don't even know how to respond to such a crazy notion. Gravity has zero impact on the diffusion of ions in seawater. That's about the nicest thing I can say about it.

stir up any substrate that has been setup for any length of time. there is organic material in it, that was not there before. if P migrates upwards, then how did this material get there?

Obviously, organic matter settled down, was digested, and the released phosphate moved up and down. No magic or rocket science.

 

[Randy Holmes-Farley]

where is the inorganic P coming from that GFO and the bacteria removed by skimming comes from? take a step back and think through the entire P cycle. using GFO, algae, carbon dosing is like using the fan in the rest room to remove the stink instead of just flushing the toilet. the inorganic P has to come from somewhere, where?

It all comes from food. Bill knows that perfectly well.

Don't have any idea what the analogy implies, but it doesn't seem very pertinent.

depends on how the tank was setup, but i would say most of the P in a newly setup tank comes from the calcium carbonate structures.

That's just totally and utterly false. One feeding ads a massive amount of phosphate.

Sorry, I don't have time to critique the rest of the comments at the moment, but I expect it is equally entertaining.

 

[Reefin' Dude]

Nothing about that statement makes any sense. Randy was talking about the process of dissolution/diffusion of water soluble forms of phosphorous in to the water column. You seem to be of the impression that chemistry and the physical world has no room for nuance or complexity. On global scales across millions of years, yes, the net effect is for phosphorous in the oceans to become sequestered in deep sediments that eventually form dry bedrock through tectonic uplifting. That's a NET effect of a spatial and temporal process measured in millions of years, kilometres of depth, and millions of square kilometres of area. In the short term, phosphorous actively moves through ALL environments, changing states, degree of availability, exchanging between substrate and solution all the time, every second of the day, everywhere on earth. Phosphorous is the 11th most common element on Earth's crust. It's everywhere. In time scales measured in weeks or months, different molecules containing phosphorous atoms that have different degrees of solubility, are subject to complex equilibrium reactions, and will become either sequestered in a substrate or liberated in to solution depending on a myriad of external factors. The scale that you keep talking about - the million year net sequestration of phosphorous in deep marine sediments operates on a spatial and temporal scale so vastly different from anything that will ever happen in any aquarium, that there is literally no point in talking about it in terms of processes taking place inside an aquarium sand bed. They have nothing to do with each other, involve different processes, different time scales, different substrates, different chemistry, different temperatures, different pressures, and different driving forces. Sand beds and deep ocean sediments aren't even made of the same stuff. Show me a single ROV video of the bottom of the ocean that shows vast fields of aragonite sand - you can't cuz there aren't any. The bottom of the ocean looks more like miracle mud than the sand people put in deep sand beds.

how does the P get there in the first place. in order for it diffuse, there must be a gradient. what starts the gradient? we keep starting a step behind. we keep talking about inorganic P. we need to start with the waste organic P. that is how the whole process gets started. it is this form of P that starts the whole sequestering of P in the marine substrates. P starts in this form, then become inorganic P only after the bacteria have started breaking it down. the same with N.

Randy was talking about Phosphorous dissolving back in to solution, therefore diffusing out in to the water column, not remaining trapped at the top of the substrate. Some orthophosphate is highly water soluble, the rest is partially soluble according external factors affecting it's equilibrium state (factors which can be manipulated by the aquarist by using products such as GFO)

again a step behind the process. we need to start at the beginning of how the N and P gets into the substrate. it is bound in waste organic material that gets worked down through the substrate. until the N and P have been released through bacterial activity there can not be an diffusion going on. by the time it does start to occur, the gradient isn't between the substrate and the water column, but more local within the substrate. with each grain of substrate acting as a barrier to diffusion with the areas around it.

Gravity has nothing to do with whether or not something is soluble in water. If you mix up a batch of fresh salt water then let it sit in a bucket for a week, the water on the bottom does not become more salty than the water on the top. If you dissolve some form of orthophosphate in to the same bucket of water and let it sit for a week, there will be the same concentration of P in the top 1cm of water as there will be in the bottom 1cm. In an aquarium where the water is being constantly mixed that's going to be even more true. It's why you can take samples of water from your sump to test the concentration of various chemicals in your display.

the waste organic material is heavier than the water. it settles to the bottom, then settles itself through the substrate. again, inorganic P and N are a step behind. if the ASW was pure SW, then you are correct. lets put some organic material into the mix. where will it be after a week? at the bottom, why? how is this not occurring in our systems, or in nature.

Sure does. Calcium carbonate also releases phosphorous under a myriad of different conditions, many of which routinely occur in a normal reef aquarium. Changes in pH and concentration of P in solution can dynamically bind or release P from calcium substrates. You can test this for yourself very easily. Go out and get some marco rock. Put it in some salt water with a known phosphate concentration. Measure that water every day for a while. I promise you, you will find the P levels will increase to a point, then they will stabilize. Now, dose that water with lanthanum chloride (or do a 100% water change), and measure the water again. The levels will probably rise, but probably not as high. You can keep doing this until the rock eventually contributes very little P to the water. It's not a one way process. The relationship between calcium and phosphate is 1000 times more complex and nuanced than you make it out to be.

the P cycle is very complex, but the basics are right there.

lets look at the Marco rock example. again, how did the P get into the rock in such a high concentration if P is being diffused out, that it is always trying to reach an equilibrium and the P is moving upwards? observational data does not show this. we have high concentrations of P in land based ancient marine substrates.

what about the role of phosphate solubilizing bacteria have in the removal of P from solid inorganic material in marine sediments.

Here's where you and I sort of agree. The romantic notion that a deep sand bed magically makes 100% of the organic matter in a system vanish in to gas is 21st century alchemy. Nature is sloppy and always has been, there is no biotic ecosystem process that recycles 100% of the material that moves through it. The only reason planet earth didn't die under it's own septic waste half a billion years ago is because the planet also has a host of abiotic processes working in the background to mop up extra organic matter, oxygen, carbon dioxide, etc. etc, a balance that life has selfishly and self-destructively screwed up multiple times in history. There will always be inert mulm left over, most of which is the unusable (to the things we keep anyway) bacterial waste (i.e., dead biofilms). I would be very interested in a detailed chemical analysis of what's actually in that stuff, and whether or not it interacts with the water chemistry at all. Generally, if something can decompose in to simpler, more available compounds, it will. The fact that that crud collects in the sand, at the bottom of overflows, in sumps, etc. and seems to stay there in that form in perpetuity makes me think it's largely inert, but I don't know if anyone actually knows what that stuff is made of.

all various types of sinks. most of these sinks are in aquatic substrates. the Earth has changed greatly over its existence from a high C atmosphere, to what it is today, well lets say a century ago anyway. as we use more sunk C stores for fuels, we are converting the Earth back to a high C atmosphere by the release of all of this bound C in the fuels. P is the same way. large amounts of it get locked up in substrates.

Good reads for sure, largely irrelevant to the processes taking place in an aquarium. They are not comparable systems.

correct! so why try? we should look at what is necessary for the organism we wish to keep and focus on that. all of the other organisms are taking resources away from the must have organisms.

For the record, I'm not advocating for deep sand beds. I wouldn't personally use one, but more because the theory behind it seems to be based more on a romanticized notion of the natural fallacy that seems to have little connection to what may or may not actually be happening. The deep sand bed methodology makes several specific claims, both about it's effect and it's mode of action. All claims about it's mode of action are based more on what we wish were true than anything that's actually demonstrable, and it fails enough times for enough people to make me think that we actually have no idea what makes them work when they do or fail when they don't.

i also am not trying to promote substrates or not. that can not be done across the board. the the must have organisms dictate that. there of course is some leeway, but one must understand how the processes work to know how to maintain the environment for their organism. if we understand that wastes collect in substrates, then it makes sense that maybe they should be cleaned out in order to maintain a low waste system. if some waste is desired, then keeping some poo as a pet is a good thing and nothing is better at keeping poo as a pet as substrate.

I'm also not saying I don't think Phosphorous is not a an issue in a reef system given it's propensity to form a bajillion different compounds and bond to calcium. I just don't think that your analogies or examples are a good model to base one's understanding of phosphorous in a marine aquarium off of.

which examples do you feel are inaccurate?

G~

 

[Reefin' Dude]

Quote:
<table cellpadding="5" cellspacing="0" border="0" width="100%"> <tbody><tr> <td class="alt2" style="border:1px inset"> Originally Posted by tmz
there must be an organism that is producing more material as waste, then it is taking in. it just doesn't work that way.
Organisms use reactive phosphate for in their structures and ATP /ADP and other needs. Inorganic and some organic phosphate may be used .As these organisms are exported or the organic compounds they produce are ,phosphate goes with them.
Some organic compounds are refractory (don't breakdown) ;some phosphate is likely sunk in some of those.
Some phosphate will bind to calcium carbonate surfaces and may return as equilibartion with the srrounding water occurs.
Some will penetrate the calcium carbonate crystal matrix and be sunk there or in bone and skeletal mass unlikely to dissolve in a typical reef tank. Phosphate is also mineralized and sunk as apatite and phosphorite and in other forms. As such reactive phosphate is reduced without tinkerbell. intervening.
</td> </tr> </tbody></table>
but none of this would occur if P migrated upwards instead of downwards.



Upwelling is how nutirents circulate into the food chain . I think you are confusing reactive and mineralized phosphate. I don't think the later will contribute significantly in a reef tank.It's sunk.

these upwellings are from the disruption of deeper marine sediments. stir the substrate on occasion for a good nutrient upwelling in the system.

the mineralized phosphates is where the problem is. we are ignoring the phosphate solubilizing bacteria again. life on earth would not exist if it were not for these little buggers. they are what keeps P on the move and not permanently getting sunk in rock. they are what release the P for terrestrial plants. they are what are around the roots of true plants.

G~

 

[tmz]

he mineralized phosphates is where the problem is. we are ignoring the phosphate solubilizing bacteria again.

What speciofc bacteria do you think scavenge significant reactive phospahte from caclium carbonate crystals? Localized acidic conditions may cause some calcium carbonate to dissolve but not very much in most tanks,,IMO and experience. Any contribution to the Pi in the water that may occur is negligable in relation to inputs from food.

 

[tmz]

where were these long ago reserves? they were old marine sediments.

In one of the papers you cited ,it is suggested they were formed in bygone geological eras when phosphate concentrations were higher. The fact that they still exist today and have not effected the level of reactive phosphate in the seas is the point. They have not dissolved or been solubilized by some mythical organism after millions of years . The reactive phosphate is sunk, essentially removed from biological activity for a very long time so far. For perspective ,I'd give the same amount of concern to apatite or phosphorite contributing reactive phosphate to a reef tank as I would to a diamond adding excess organic carbon.

 

[Reefin' Dude]

edit: I see others already addressed these points, but I'll leave them here anyway...

because land life wouldn't exist. if P did not get locked up in substrates, then there would not be a mechanism for P to become available for land based organisms, it would all become locked up at the substrate water interface. look at any phosphate cycle. they all have P being locked up in marine substrates, then exported by terrestrial upheavals.

Sorry, I don't have the slightest idea what terrestial upheaval has to do with sand beds releasing posphate back into the water column.

if P is not sunk in marine substrates, but is always reaching equilibrium from above, then how can P get recycled back to terrestrial areas?

Do you doubt it happens?

absolutely not. some of it does occur, but i would put more of the release from bacteria working on the mineralized P, and not from diffusion. if equalization was the stronger force, then trophic levels would be much more consistent. with the highest concentrations being at the substrate water interface.

Variable rates of phosphate uptake by shallow marine carbonate substrates: Mechanism and ecological significance.

Obviously there is phosphate present in marine deposits. That doesn't mean that all or even most of the phosphate that enters the substrate as organic matter ends up in the deposits permanently.

if there is more P in the substrate than when it started, then it is a sink. it really doesn't matter if it just a little or even all of it. the amount of P is increasing, it is not being exported as fast or faster than it is accumulating.

what would the benthic organisms eat? if all of the P is at the top of the substrate, then what would the organism deep in the substrate eat? they need resources also.

Digested organics release inorganic phosphate, and that released ion moves up and down, and some leaves the sand for the water. Noting is starved by that process.

digested by what? back to the bacteria. until the solid organic waste is broken down by the bacteria there is not any inorganic P to move. the more organisms that may have eaten a waste product from another organism that lives in the substrate is going to release waste also in the substrate. any of these wastes that make it into the substrate are not going be able to move very far.

how many P compounds are lighter than water in our systems? gravity doesn't work that way.

Wow, I don't even know how to respond to such a crazy notion. Gravity has zero impact on the diffusion of ions in seawater. That's about the nicest thing I can say about it.

sorry, i wrote that quickly. i was again talking about solid waste material.

stir up any substrate that has been setup for any length of time. there is organic material in it, that was not there before. if P migrates upwards, then how did this material get there?

Obviously, organic matter settled down, was digested, and the released phosphate moved up and down. No magic or rocket science.

an increase in total P in the substrate occurs. you are correct, not rocket science or magic. the only inorganic P that gets to be released into the water column is any that is left over from any other organisms that also want it. other bacteria/micro algae/cyano will quickly uptake any. again keeping it within the substrate.

where is the inorganic P coming from that GFO and the bacteria removed by skimming comes from? take a step back and think through the entire P cycle. using GFO, algae, carbon dosing is like using the fan in the rest room to remove the stink instead of just flushing the toilet. the inorganic P has to come from somewhere, where?

It all comes from food. Bill knows that perfectly well.

no, from the waste products of the organisms in the system. very little is from the breakdown of the food we put into the systems, that gets used up quickly by the organisms we are feeding. all of those hamburgers rear their ugly head again. if there are organisms eating waste, then there needs to be that waste to begin with to support the organisms. it is a pyramid. as you move down the food chain more and more material is needed. we as hobbyists ignore the waste products and believe that something else will eat it all. that is not the case and these waste products count in the total N and P that make up the trophic state of the system. we tend to focus on the things we can test for, but ignore the entire P and N picture.

Don't have any idea what the analogy implies, but it doesn't seem very pertinent.

the analogy is representing the fact that we are worrying about the inorganic P (the stink) when we should be worried about the organic P (the poo in the toilet). GFO, carbon dosing are all going after the inorganic P and not the source of the inorganic P, the waste products from organisms. remove the wastes and remove the source of the inorganic P, no need for the fan to remove the stink.

depends on how the tank was setup, but i would say most of the P in a newly setup tank comes from the calcium carbonate structures.

That's just totally and utterly false. One feeding ads a massive amount of phosphate.

who says you need to add food? try just adding an N source. the P is already there.

we mine P from calcium carbonate structures. Post #23 in this thread though the entire thread is helpful.

Sorry, I don't have time to critique the rest of the comments at the moment, but I expect it is equally entertaining.

i am sorry you find this so entertaining.