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

[JPMagyar]

I have been engaged in a great discussion on another thread, but I felt that the topic was not properly defined so I decided to start a new thread dedicated to the topic.


Here is the question:

Are Deep Sand Beds dangerous to use in a marine aquarium and if so why?


This is meant to be a friendly debate and anyone taking part should remember that this is just a hobby, and we are all here for the same reason because we want to share our experiences and make each other's tanks better. In that light, please refrain from personalizing any comments.

So who wants to get the ball rolling


Joe

[Fishmommy]

Can you define "deep" please for us noobs?


Sent from my iPad using Tapatalk HD

[JPMagyar]

Excellent point:

Let's start with some definitions:

deep = more than 3 inches
sand = marine substrate of 2 mm or less

[power boat jim]

Trust me when I say I have read nearly everything out there on the topic and the questions I pose are not for me, but rather just to show what it means to be scientific.

Here is a quote taken from the article you referenced. The authors are very careful to distinguish between the known danger of hydrogen sulfide and the HYPOTHESIS that a DSB may pose a danger.




A DSB MAY be dangerous. It remains yet to be proven scientifically.


Joe


That might be true. However, if an experiment or a condition can be repeated using the same conditions by numerous parties and the same results are incurred, that is a good basis for fact. Here I believe all we are saying is detritus builds up in the sand, it decays eventually producing H2s, the sandbed is disturbed releasing a toxic low pH gas into the tank possibly killing inhabitants. All of this has happend and certainly could be made to happen in a lab if someone really wanted to spend the time.Which part of this hasnt been or cant be proven scientifically many times over?

Im, just looking at the chain of events, all them are solid scientific fact. I believe you want numbers, times and levels put to them? am I correct?

I believe the author didnt make the connection since that was not in the scope of the paper. He did, in my opinion leave enough evidence that its a given, sandbeds under the right conditions, can certainly be a hazard.

I took this from the other forum.

[Paul B]

I think that if you are looking for scientific literature you may be waiting a long time as this is a hobby and there are no experts, as there are no degrees for a hobby. These are also classified as "ornamental tropical fish" and not food fish so again there will be no Government studies.
I think we should rely on hobbiests such as are here to tell us how long their DSB lasted and if it didn't last, why not, what happened to it.
How many people here ran a DSB and how long did it last?

[JPMagyar]

Originally Posted by power boat jim

That might be true. However, if an experiment or a condition can be repeated using the same conditions by numerous parties and the same results are incurred, that is a good basis for fact.

At one point in time everyone went outside every morning and said "the sun comes up and goes down in a circular pattern so it must be traveling around the Earth", and at the same time they also said "where ever I look the Earth is flat so it must be flat and the ocean is the limit". Just because a tank has a) a DSB and b) a loss of livestock does not mean that that ALL DSBs are dangerous. How many tanks with DSBs have you personally witnessed lose livestock? How many anecdotes are there on RC of tanks with DSBs that lost livestock? Dozens, hundreds? There are tens of thousands of RC memebers and many thousands more aquarium owners not represented on RC. How many have DSBs and what is the loss rate? We simply do not know, but I am certain that the anecdote rate is not enough to say unequivocally that all DSBs are dangerous.

Here is the heart of my issue. I give you 2 statements and see if you would agree with me that one is simply not true.


Statement A:

All DSBs in a marine aquarium will eventually become toxic and lead to the loss of some or all livestock and this is a fact therefore a new aquarist should NOT use a DSB ever.


Statement B:

There is some evidence and logic to suggest that some DSBs may have the potential to become toxic but we know very little as to the mechanism that makes them dangerous and whether or not this applies to all DSBs therefore a new aquarist should research and understand why they are using a DSB and how it is supposed to work if they chose to use one.



Joe

[JPMagyar]

A couple other quick notes:

I'm working on a history of Deep Sand Beds for any newer folks following along, and how do you guys feel about giving up a brief bio and introduction for those wanting to take part in the debate. Is that helpful or pointless?

Also I'm looking to refine the debate as well because the main issue here is more one of semantics I think. I don't think it's fair for anyone to represent to a newbie that all DSBs are bad, but I need to find a more precise way to frame the question.


Joe

[power boat jim]

Originally Posted by JPMagyar

At one point in time everyone went outside every morning and said "the sun comes up and goes down in a circular pattern so it must be traveling around the Earth", and at the same time they also said "where ever I look the Earth is flat so it must be flat and the ocean is the limit". Just because a tank has a) a DSB and b) a loss of livestock does not mean that that ALL DSBs are dangerous. How many tanks with DSBs have you personally witnessed lose livestock? How many anecdotes are there on RC of tanks with DSBs that lost livestock? Dozens, hundreds? There are tens of thousands of RC memebers and many thousands more aquarium owners not represented on RC. How many have DSBs and what is the loss rate? We simply do not know, but I am certain that the anecdote rate is not enough to say unequivocally that all DSBs are dangerous.

Here is the heart of my issue. I give you 2 statements and see if you would agree with me that one is simply not true.


Statement A:

All DSBs in a marine aquarium will eventually become toxic and lead to the loss of some or all livestock and this is a fact therefore a new aquarist should NOT use a DSB ever.


Statement B:

There is some evidence and logic to suggest that some DSBs may have the potential to become toxic but we know very little as to the mechanism that makes them dangerous and whether or not this applies to all DSBs therefore a new aquarist should research and understand why they are using a DSB and how it is supposed to work if they chose to use one.



Joe

Neither statement is entirely true.As far as #1 goes, In this hobby I dont know of too many things that you can say will happen 100% of the time. There are far too many variables from one tank to another to make assumptions on how people are actually running them.

As far as #2 is concerned its not true either. Plenty is known about what mechanism makes a sandbed toxic. Its just a question of will the parameters that cause it to go belly up appear in every single application.

I will agree that if you are going to use one be aware of what can happen

By the same token, what evidence is there that these things actually work? What studies have been done that show when the bed has been added to a system the nitrate levels actually came down and it could be attributed directly to the sand?

[Paul B]

By the same token, what evidence is there that these things actually work?

Anybody with a 10 year old DSB raise your hand..............higher
Anybody who ran a DSB for less time than 10 years and something happened to kill your fish, raise your hand. And if this is you, what happened to the inhabitants if anything.

I feel that even if a DSB does not add anything toxic to the tank, after so many years it just stops doing anything and may as well be concrete. But I don't know unless we hear from people who had problems and people who don't have problems, "in ten" years not 10 months.
Besides working, it should work for a substantial time as even a bare tank with nothing at all in it will support life for a while.

[JPMagyar]

Early reefkeepers struggled to keep nutrients from building up in a home aquarium until the discovery of the Berlin System then in the 1970s and early 1980s German aquarists became noted world wide for being able to grow so called stony corals using large amounts of live rock. It became evident that the live rock was acting as some type of natural filter. Unfortunately this was not useful for large public aquariums so a brilliant French aquarist named Dr. Jaubert came up with a new method of filtration using a plenum which was made famous by a coral display he helped create at the Monaco Aquarium. The so called "Moroccan Display" featured wonderful corals and used the new plenum style filtration named after Dr. Jaubert, the Jaubert Plenum. This concept led to experimentation with other substrate filtration and given the success with live rock it wasn’t long before aquarists were experimenting with “live sand”. Then in 1991 two well known US experts published a book called Dynamic Aquarium which popularized the idea of adding sandbeds in a marine aquarium as a means of filtration and buffering. The basic concept requires creating a sand bed filled with micro fauna that keep the sand “biologically active” and not just dead sand, therefore allowing for gaseous exchange and continual filtration of nitrogenous waste. Ever since that time the efficacy of sand beds, there depth, and the usable materials have been hotly debated amongst the top biologists. Within the US the popularity of DSBs has remained fairly constant over that time; while European aquarists have not taken to the concept quite as readily and have divided more equally among plenum style, bare bottom, and DSBs. Then in January of 2003 a well known member of RC and noted biologist, Dr Ron Shimek, wrote a series of articles and a pamphlet which popularized the DSB here on RC. There ensued many a debate surrounding the theory of DSBs and their efficacy, and soon after Dr. Shimek stopped contributing to RC. Since that time the debate surrounding DSBs has continued, but suffice to say there are thousands of DSBs in use today and plenty of well known proponents, like Anthony Calfo, and an equal number of detractors.

So that kids is DSB history in one paragraph or less!

[JPMagyar]

Originally Posted by Paul B

Anybody with a 10 year old DSB raise your hand..............higher

Anthony Calfo claims he has setup hundreds and maintained them for more than a decade.



For that matter, anybody with a 10 year old aquarium here on RC raise your hand. I think the sample would be quite small.

[JPMagyar]

Originally Posted by power boat jim

Plenty is known about what mechanism makes a sandbed toxic.

What exactly is known, and how do you "know it"?

Originally Posted by power boat jim

Its just a question of will the parameters that cause it to go belly up appear in every single application.

Yes, this is exactly my point. We do not have an answer to that question, but we do know 1000s upon 1000s of DSB are in existence.

[Paul B]

So that kids is DSB history in one paragraph or less!

Yes it is (I actually speak on the history of the hobby)
But it was Robert Straughn in the 1950s who advocated live rock, but he didn't understand the bacterial facet of it and considered the aiptasia anemones on the rock to somehow add healthful benefits to aquarium water. (I still have his book)
He didn't call it live rock, "but anemone rock"
Unfortunately in the early 70s we tried to keep aiptasia in our tanks but could not. I used to buy aiptasia and try to get them to live in my tank, but from all the copper I had to use, the things would not live. All fish had ich, there were no reef tanks and what we had were not very healthy so coper had to stay continousely in the water. There was no liquid copper so we used pennies, 20 to the gallon and when the fish would lie on the bottom, we knew to remove some pennies, about five cents.
So that is also a little history.

[Paul B]

Anthony Calfo claims he has setup hundreds and maintained them for more than a decade.

Anthony may be one, I don't know if he had to do anything to those beds but how about anyone else?
Remember I run a UG filter and my tank is very old, does that mean we should all run UG filters?

[power boat jim]

Originally Posted by JPMagyar

What exactly is known, and how do you "know it"?


Yes, this is exactly my point. We do not have an answer to that question, but we do know 1000s upon 1000s of DSB are in existence.

I answered this at least twice, read the part about a dsb being an anearobic digester. I have 21 years at a sewage treatment plant, believe me its a proven fact about what happens to sludge when it decays in a pile under water. You can fill the tank with holy water if you want but it want but the detritus isnt going anywhere unless you remove it from the system.


I have no way to know how many. I do know 100% of the one I had failed after 18 months. It clogged with poop and released H2s into my system. My pH was 7.3 when I took it out. Been 8.3 ever since.

[Bilk]

Wasn't sure which thread to post to as I believe they're really dealing with the same knowns and unknowns on the subject of substrate or no substrate.

I believe everyone who does or has kept a captive reef realizes there is no magic bullet. There's no magic in a bottle and there's no magic formula to the perfect reef tank. If there were, then someone would already be marketing it. If it were so easily repeatable, then it would be an off the shelf product. I think if everyone that's presently keeping a successful system (relative term by the way), would honestly have to admit that even if they duplicated their system down to the coral, things might not work out the same way in the duplicate tank. There are just too many variables. Duplicate conditions might be achievable in small controlled experiments in small containers, but when the system grows to larger scale, the variables multiply exponentially.

I understand the perspective of those from the BB side of the argument. If there's no substrate then one can clearly see there is no sediment and if there is, it can easily be removed. In re-establishing my system, I had this debate with myself repeatedly. My thoughts were, BB would be an easier system to maintain and thus, I'd be more inclined to follow through with easier maintenance rather than maintenance that took more effort.

At present , my system is cycling with a shallow sand bed of a mix of fine and special grade aragonite. My idea behind using the fine with the larger grain sand is the fine will act as a base and a binder for the larger grain sand, settling in between the larger grains like a loose bed mortar. Kind of how patio blocks might be set. I chose to have sand because I like the look of it vs a bare bottom. But, I also chose it because I believe there are benefits derived from it for the system. My hope is that the mix of fine and large grain sand will be a bit more dense and compacted and will not allow detritus to settle down into the bed and thus will not become the nutrient sink that many on the BB side believe it does become. I hope I made the better choice.

In many ways the choice was based on my prior experience in keeping a tank with corals. I had a 110g with a DSB and a plenum. It ran for almost ten years. It was my first and only tank, and being such there were certainly ups and downs as everything was a new learning experience and well this was back in the 80s and things in the hobby, as most of you know, were more unknown than they are now and that isn't saying much. I think the idea that this topic is still being debated is proof of that.

That system ran well and thrived. Corals grew and fish and shrimp even spawned in the system. I had a carpet anemone grow from 4" in diameter to almost 12". As Joe says he does, I used to make a storm in the tank, blowing the top of the sand only and all of the rocks, liberating detritus. So even in a BB tank, there is a buildup of detritus and if the keeper doesn't liberate it from the rock, well then "poo" or what ever organics that are particulate in nature, including the microfauna that have died within the rocks, will contribute to the bio load and build up even when water changes are performed. The nasty stuff has to be removed no matter what is or is not on the bottom.

Well that tank did eventually crash, but it was due to moving the tank and everything within and not handling the substrate properly. Back then the belief was keep the substrate as it is the biological filter. So I bagged it up like the rest of the livestock and reused it in the new location. I put everything back the way it was. Then we went on a 2 week vacation. Bad timing for that. I left a friend in charge and he had no experience nor any way of knowing if something was going wrong. Upon returning, I found the whole system in decline to the point it wasn't salvageable. That tank became a terrarium for a few years

What I find interesting in reading again about the hobby and in doing research is that little has changed on this front - the substrate argument. I read somewhere that many of the aquariums still utilize a plenum in their reef tanks. Can anyone verify this? If so, they are obviously well educated on what does and what doesn't work. Heck, maybe I should use a plenum :O LOL

Ah well, it's a rewarding hobby when things go well and it really sucks when it doesn't

Edit:

I was able to scrounge up one pic of my old 110g and scan it. It's the left side of the tank only, but it did look pretty

[Death Shrimp99]

Why not just use macro algae like chaeto or caulerpa to export nutrients? There's no debate that the chaeto method works and it's been proven to be efficient at it. It's natural, cheap, and easy.
Even if you want to be stubborn and keep defending the old deep sand bed method, say you prove somehow that it doesn't cause tanks to crash eventually or a remote DSB removes the risk of a tank crash, now is it even better at exporting nutrients as the chaeto method? What advantage does it have over it?

What i'm getting at here is this... forget about even proving or disproving weither it will eventually cause a tank to crash, compare it with other alternatives such as chaeto as a solution to the nutrient export problem. Do the advantages outweigh the disadvantages? IMO, definitely not. I don't see any advantage of of DSB over macro algae except maybe the fact that you need a fuge to use the macro algae method, but you would need a big bucket or something simular to a fuge for a remote DSB anyway, or extra vertical space in your main tank.

[elegance coral]

Crunched for time, but here's something you may find interesting.
https://www.google.com/url?sa=t&rct=...b4i0lqu9hCv3Yw

https://www.google.com/url?sa=t&rct=...43148975,d.eWU

[Dre59]

Another great thread!!! Mine has been going 2+ years already.. On my new build might try a RDSB vs using my DT.. Less money :banghead: I do buy monthly a few snails to keep the DSB air pockets mixed..

[JPMagyar]

Originally Posted by power boat jim

I answered this at least twice,

I have 21 years at a sewage treatment plant, believe me its a proven fact about what happens to sludge when it decays in a pile under water.

My apologies for not drawing the connection to your earlier comments. I have pulled quotes from what I believe you were referring.

Originally Posted by power boat jim

Lets call a DSB by what it really is, its an anaerobic digester of sorts. It breaks down biomass (sludge), by using microbes, into a different somewhat more metabolized form of waste. The byproduct of this tranformation leaves you with some unpleasent "substances" including methane, hydrogen sulfide maybe some carbon dioxide.

Your hypothesis based on your life experience and knowledge leads you to believe that organic material will sink into a DSB and create these byproducts which will then lead to a loss of livestock.

Other noted scientists have written extensively explaining their hypothesis that such organic material will remain in suspension due to the high flow rate found in many marine aquariums and so the organic material will be removed as a matter of routine maintenance and skimming thereby allowing the sand bed to remain biologically active.

These are both just HYPOTHESES untested using the scientific method and both based on logic and science, and examples exist of BOTH healthy DSBs and stinky, sludge filled DSBs. Why? We don't know.

Originally Posted by power boat jim

The fact also remains that there is very little reduction in the biomass during this tranformation

Can you quantify how much biomass remains from feeding 10 fish? Is the biomass leftover from herbivorous fish the same as that left by carnivorous fish? Are any of these byproducts different from the byproducts created when human waste breaks down, and are they water soluble to the extent they may readily remain in suspension long enough to be removed by a skimmer and prior to becoming submerged in a DSB? If biomass does accumulate what is the rate of accumulation, can that rate vary from tank to tank, and how long will it take at the maximum rate of accumulation before enough hydrogen sulfide is formed to create a deadly release of gas. 1 year, 5 years, 50 years? We don't know. It's never been studied using the Scientific Method, and any statement you make to the contrary is a HYPOTHESIS, and the fact will still remain that healthy tanks with DSBs exist.

Originally Posted by power boat jim

If people have had dsbs working in their tanks for a long time they are physically exporting biomass in a different manner.

There is no IF in people with DSBs that are more than a couple years old, and yes the "biomass" is being exported somehow, but that's just it we don't know how that is happening nor can we likely ever come to a simple answer because the variables between the thousands of tanks are far too many. All we can say is that some people with DSBs are making it work.

So, I go back to my fundamental issue.

No one can say unequivocally that all DSBs will end up as toxic killers of livestock nor can anyone say unequivocally that DSBs can be maintained forever as healthy biologically active nitrogenous waste treatment plants.


DSBs MAY be bad, but we don't know that as FACT.





The following is taken from an Advanced Aquarist article on DSBs and is the heart of my argument:

. . . aquarists across the world have spent countless hours arguing the relative pros and cons of various aquarium designs. Passion for our hobby is good, but these arguments are meaningless and a waste of time; it is impossible to make an informed decision on the best way to set up an aquarium without real DATA to evaluate how different options perform. It is critical to have data because there is always variability among experiments (see Fig. 2). A given outcome is only predictable if the variation within treatments is less than the variation from one treatment to the next. We know this may not make sense right now, but let's work through a simple example to explain why it is so important. Let's say you set up one tank with a canister filter and one tank with an undergravel filter and find that the tank with the canister filter looks best. From that point on, you try to set up the exact same system ten times, and some of them look better than the original and some look even worse than the original tank based on the undergravel filter. If there is that much variation from one tank to the next, it is impossible to say for sure that the differences between the filters actually have anything to do with the ultimate success or failure of your aquarium. This may sound like an extreme example, but this is exactly what happens in reality and is clearly demonstrated in our experiments. Even in the lab, identical aquariums set up from a single well-mixed pool of gravel and seawater without any live animals in them show a dramatic amount of variation among trials (Fig. 3). I'm sure you can imagine how much more variation there would be among tanks set up by different people in different locations and with different materials and animals! It is only by having properly replicated experiments that we can evaluate whether the treatment itself has any effect . . .

Thanks for taking the time to discuss such a great topic and providing superb incite!



Joe

[gbru316]

Originally Posted by JPMagyar

Other noted scientists have written extensively explaining their hypothesis that such organic material will remain in suspension due to the high flow rate found in many marine aquariums and so the organic material will be removed as a matter of routine maintenance and skimming thereby allowing the sand bed to remain biologically active.

I'm not sure how they can present this hypothesis, even those with extreme flow rates (I have between 175x and 200x) notice detritus settling. If I don't get the turkey baster out weekly, I end up with detritus pockets in my live rock.

I'm all for the scientific method, my career is based on science and physics, but I see no reason to test this scientifically. Unless one can implement high flow rates in every single location in an aquarium, there will be settling of organics. I have so much flow that I cannot use sand, yet detritus still settles. As such, if I reduced flow to an amount that allowed for substrate, I would surely have settling as well.


It's actually pretty easy for many to see, firsthand. Anyone with a stand that allows them to see the bottom of the tank can take a flashlight and view the bottom of the substrate from underneath. If the tank has been running for any length of time, a brown sludge will be visible.

[keithhays]

I think it is extremely difficult for hobbyists to run the type of experiments with controls required to answer any particular question in the hobby, nor are most inclined to do so. Having said that there are some who have gone to a lot of work in some areas such as light and specific water chemistry. DSB's or the lack or one are not necessarily an easy thing to test for and you would have to ask a much more specific question rather than "are they dangerous". Many things are dangerous, many corals for instance are dangerous to some.

Normally, in other industries business will employ science at a very minimum to make sure that actual products are not dangerous, you will see very little of that in this hobby. If scientific experiments were performed to either prove or disprove any particular theory of marine reef keeping or even just fish keeping, many products would cease to exist. There is no incentive for anyone to do such a thing.

One place where the business of fish keeping and science are used as a necessity is the limited area of marine food fish keeping. Because loosing fish in that industry affects the bottom line and also have many controls after the fact, more information can generally be found in that area.

I personally have a tendency to look at the overall hobby as a sort of giant scientific study which ultimately produces a result that is healthier for the animals kept in the systems. The problem arises in being able to communicate those results in the short term effectively enough to replicate any particular success. Frequently, the aquarist of hobbyist won't really know why it happened and quite frequently attributes the success to the last thing they did, the first thing the did, etc. When that is communicated out of course success is not had by all.

In general, I have found it more useful to look to the long term trends in the hobby rather than to the short term sort of fashion or fads that pop up. In the IT world I work in, there is a concept known as the "bleeding edge", I prefer to let other people bleed first in most cases.

Just to keep up with tradition, DSB's in my opinion are not inherently dangerous, but can be made to be if left deployed for too long a period of time.

[ahud]

So for the people that are pro DSB. The belief is that we can continually add mass into these piles of sand and the mass somehow disappears? I think that is the assumption you have to make if you believe a DSB will work 10+ years with no maintenance.

I was amazed and excited about the idea of a DSB. But when you look at it from a logical stand point, they do not make sense. Even some of the big time proponents of DSB could not make them work. How do you keep them from absorbing phosphates and leeching them back into the system?

I'm choosing to go with a shallow sand bed and siphoning off the stand during water changes. I think sand offers no other benefits other than aesthetics and offering a home for burrowing fish/inverts.

Here is an awesome thread IMO that discusses it in greater detail:
http://www.thereeftank.com/forums/f6...ed-160389.html

[elegance coral]

Originally Posted by JPMagyar

Your hypothesis based on your life experience and knowledge leads you to believe that organic material will sink into a DSB

We need not "believe" that organic matter will sink into a DSB. "Belief" should be reserved for religion. Not science. The basic laws of physics tells us that organic matter sinks. Organic matter is typically heavier than water. Therefore, it sinks. We do not need a dedicated scientific experiment to show this. The science involved is well known and well understood. To "believe" differently is to simply be wrong.

If you must have an experiment to show this process, it's simple. Take two white buckets and a gravel vac. Siphon water from the mid water level of an aquarium, into bucket "A". Then siphon water through an aged Shemik style DSB, using the gravel vac, into bucket "B". We can not see through organic matter. The bottom of bucket "A" should be clearly visible due to the lack of organic matter. Bucket "B" will be so choked with rotting organic matter that the bottom of the bucket is not visible. The sand was clean when it originally went into the aquarium. How did the organic matter get in the sand? . It didn't just magically appear. It settled, and accumulated there due to the well know laws of physics. This isn't arguable. It can not be disputed. It is fact.

and create these byproducts which will then lead to a loss of livestock.

Again, this is well known and well understood science. One organisms waste is anothers beneficial nutrients. This is the process that makes life possible on this planet. Our waste is toxic to us, but not to some other organisms. We must separate ourselves from our waste or die. If your kidneys fail, you're dead, because you are no longer able to separate yourself from your waste. If you relieve yourself in your bedroom, and allow your waste to accumulate there, you're likely to get sick and die. If you relieve yourself on your lawn, you're likely to have some lush green grass, because the grass is able to utilize your waste as beneficial nutrients. If we force our pets to live in a tiny glass box with six inches of their own waste accumulated on the bottom, they're likely to get sick and die. This is nothing new. It's well understood. We clean the bottom of every other small container where we keep living animals. Hamsters, birds, snakes, humans in jail............... you name it. If we do not remove an animals waste from the small container where they live, they are highly likely to get sick and die. This is fact. It is not arguable. This is not a "hypothesis". This is not a theory. This is well known fact. To "believe" otherwise is simply absurd.

Other noted scientists have written extensively explaining their hypothesis that such organic material will remain in suspension due to the high flow rate found in many marine aquariums and so the organic material will be removed as a matter of routine maintenance and skimming thereby allowing the sand bed to remain biologically active.

Who are these "noted scientists", and where is their work?
There is no scientist, worth their salt, that would make such a statement.
If the flow is slow enough to allow the grains of sand to remain stationary on the bottom of the tank, it is also slow enough to allow particles of organic matter to settle and accumulate there as well. You would have to increase flow, to the point that inorganic particles could not remain stationary, to prevent organic particles from becoming stationary. Stationary particles of sand obstruct flow, slowing it to the point that organic particles carried into the sand with that flow, settles and rots. The only way to prevent this, would be to increase flow to the point that sand itself was no longer stationary.

examples exist of BOTH healthy DSBs and stinky, sludge filled DSBs. Why? We don't know.

What is your definition of a "healthy" DSB? And healthy to who?

It's been explained before. A sand bed that is deep, need not be "unhealthy". We simply need to keep it clean. A sand bed, as Shemik describes it, where we allow "sludge" to build to the point that it supports hundreds of thousands of sludge eating organisms, will becomes unhealthy for the pets we purchase.

Can you quantify how much biomass remains from feeding 10 fish?

Why is that relevant? We know that the more biomass we have in a system, the harder we need to work to keep the system clean and healthy. The lower the biomass, the longer the tank will remain healthy without our intervention. We really don't need to put a number on the amount of biomass produced from feeding "X" number of fish. We simply need to understand the importance of keeping that number as low as possible.

Is the biomass leftover from herbivorous fish the same as that left by carnivorous fish?

No, but again, it's really not relevant.

Are any of these byproducts different from the byproducts created when human waste breaks down,

Not any more different than the rest of the animal kingdom. The waste produced will vary from species to species and from day to day. The waste I produce today will be different from the waste I produce tomorrow. I seriously don't see where this is relevant though. All of this waste material contains many different elements and compounds. As this waste breaks down, the substances it contains will be altered and released back into the environment. These substances are beneficial to some, and toxic to others. This is one of the reasons we have different habitats in nature that support different forms of life. Mangrove swamps have high concentrations of these substances, due to the large amount of rotting organic matter in the sediments. There are times you can smell a mangrove swamp from miles away. The organisms found in mangrove swamps differ greatly from those found on healthy, growing, coral reefs. The concentration of substances released through decomposition are very, very, very, very, very, low on these healthy coral reefs. This should be a HUGE red flag to anyone attempting to keep coral reef creatures in a tiny glass box. Keep large amounts of rotting organic matter in the tank, and you create something that resembles a mangrove swamp. Remove rotting organic matter and you're more likely to create something that resembles a healthy, growing, coral reef.

If biomass does accumulate what is the rate of accumulation, can that rate vary from tank to tank,

Yes. The rate of accumulation will, or can, differ greatly from one system to another. However, the rate of accumulation is irrelevant. If I drive to work a 50 MPH, I'll get there quickly. If I drive 5 MPH, I get there slowly. It doesn't really mater because I end up at the same place. If I accumulate one cubic CM of rotting organic matter in my sand per week, it may take quite some time before it becomes unhealthy for my pets, or causes me to invest in a larger skimmer. If I accumulate ten cubic CM's of rotting organic matter in my sand per week, it will become unhealthy much faster. I don't need to have a number to represent the rate of accumulation. I simply need to understand that I need to limit that accumulation, and/or take steps to offset the negative effects of that accumulation.


We know that it accumulates, not only because we see it with our own eyes, but because we typically feed at a rate that exceeds the rate of decomposition. In other words, if we feed a cube of food, we typically feed another cube before the first cube has a chance to completely decompose. A portion of that food will end up in the sand bed even if we have an incredible filter system.

Nature is great at supporting massive amounts of life, and creating very nutrient rich environments, with very little nutrient inputs from outside sources. In our system, what starts out as a little detritus in the sand bed, can become a nutrient laden swamp, if we do not intervene to stop this process. Bacteria will take up nutrients from that detritus and reproduce. Bacteria can be short lived. When they die, their tissues are added to the rotting organic matter in the sand along with the small amount that gets there through the food we feed. Now the living bacteria are utilizing nutrients that originate from the foods we feed, and the tissues of their dead relatives. As this process grows, the amount of nutrients being released into the system water grows. It begins to fuel algae and microbial growth in the rocks above. When these organisms die, they fall into the sand, where they rot and fuel more growth/reproduction. As the amount of organic matter grows, it begins to support larger animals like worms, and mini crustaceans/pods. These organisms don't typically live long either. They grow, reproduce, and die, just as the algae and microbes do. Through this process, nature is able to recycle nutrients in one area, increasing the nutrient content of that area, even when the input of nutrients to that area is very low. This is clear to see in photos of Shemik style DSB's. There is an abundance of life in these sand beds. Everything from cyanobacteria, worms, pods, algae, and countless little critters not viable with the naked eye. This proliferation of life could not be possible if it relied solely, and directly, on the food being added to the aquarium on a daily basis. It's only possible due to natures ability to retain and recycle nutrients in one area. In a Shemik DSB system, on day one, everything is clean, and the nutrient level of the system is low. As time progresses, the nutrient level within the system continually climbs. The common scenario in these systems is for the filtration and maintenance to cope with this pollution for a period of time. The health of the system is constantly being degraded, but the filtration and maintenance handles it. Eventually, the system reaches a point where the production of harmful substances from rot and decay overwhelm the filtration's ability to keep those levels low. This is when animals die. People declare the system is suffering from old tank syndrome, and needs to be started over. Often, the hobbyist "belief" in this system is so strong, they break down the system, and rebuild it, doing the exact same thing again. This only leads to more animals dying, and thousands of dollars needlessly spent.

and how long will it take at the maximum rate of accumulation before enough hydrogen sulfide is formed to create a deadly release of gas. 1 year, 5 years, 50 years?

While hydrogen sulfide is a reasonable concern when talking about harmful substances from decaying matter, it isn't needed to cause illness and death in our systems. Any number of elements, compounds, or combination of substances released/produced through decomposition can reach harmful levels when you have six inches of rot and decay on the bottom of the tank. Most elements are at trace levels on coral reefs. Some down to the parts per billion.

and the fact will still remain that healthy tanks with DSBs exist.

You have stated that this is not evidence proving DSB's are beneficial, yet you keep bringing it up, and even posting pic's of tanks with DSB's, as if it proves something. It does not.

Most people would agree that dumping liquid fertilizer, full of nitrogen, phosphorus, and heavy metals into a reef tank would be a bad idea, and put the lives of the inhabitants at risk. However, I could hook up a dosing pump to dose such a fertilizer into my system, and still have a seemingly healthy and thriving reef display. I simply need to employ methods to remove that fertilizer at a pace that keeps the concentration of harmful substances below problem causing levels. The question is, why would I do that? The fact still remains that such liquid fertilizers would be harmful to coral reef tanks. Six inches of rotting organic matter on the bottom of a tank will release fertilizers like nitrogen, phosphorus, and heavy metals. Just like the liquid store bought fertilizers. So, the question is, why would I put such a sand bed on the bottom of my tank?

All we can say is that some people with DSBs are making it work.

No. We can not say that. The fact that they have a DSB, and all their animals haven't died, is not evidence that a DSB works. Shemik and his disciples have made some outrageous claims about the magical abilities of their DSB systems. If a DSB does not preform these tasks, they do not work. If I pile up a bunch of scrap metal in my front yard, and claim it to be a rocket ship to the moon, can I claim that it works if it can not fly to the moon? Of course not. It's just a pile of junk in my front yard. This DSB does not perform the tasks claimed of it. Therefore, it does not work. It doesn't matter that a DSB hasn't killed every living creature in some tank somewhere. It still does not work. It's still nothing more than a six inch pile of rot and decay full of worms and bugs.


Peace
EC

[Paul B]

Elegance, that is one of the longest posts I ever read, but well worded and a nice read.
You mentioned mangroves, I was in one last week and took a picture. It doesn't have anything to do with this thread but I decided to put it in anyway just to show a mangrove.
Have a great day.


Place was crawling with Casiopia.