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

[billsreef]

you are supplying nutrients to support organisms that are not your must have organisms.

Based on this conversation, I'm assuming the benthic sand bed critters are the "not your must have organisms". In this case, you are making an incorrect assumption about extra nutrients being added to support them. Those "not your must have organisms" are existing the same nutrients being added to feed the "must have organisms", aka the fish and the corals. It's not a matter of adding yet more, but simply the sand bed critters (I'm including everything from the bacteria on up) taking up the nutrients that result from the inevitable feeding of the tank. There are no extra source of nutrients just because of having a sand bed and associated critters. While there is certainly P bound up in those organisms, it is bound up in them and unavailable until they are consumed by something else, and so on and so forth. As unavailable and bound up, they totally irrelevant in terms of contributing to the P that can cause issues in our tanks...in fact, they help by taking up the P and removing it from the water column, giving us more time to deal with ultimate removal by whatever means you like.

 

[Brummie]

Anyone applied ochams Razor to this? Seems it's very complicated. I got a DSB of silica for 10 years, what's the problem?

 

[billsreef]

I got a DSB of silica for 10 years, what's the problem?

I don't know. But give it some time, and someone will come along and explain the problem to us

 

[reefwars]

I don't know. But give it some time, and someone will come along and explain the problem to us

lol that just made me laugh :uzi:

 

[tmz]

Hey Paul,

I still think your rugf system is worth a serious look . It has always interested me. Pushing water up through the substrate may be an improvement to diffusion advective flow and sand critters to move nutrients to the bacteria , now that we know we don't have to fret about denitrifying bacteria dying when exposed to oxygen..
I think the beer can is probably a bad idea though.

 

[saf1]

Setting aside the argument of whether detritus is mostly inert, or not, the physical aspects of this material are at least equally important, IMO. Out in the open, such as in a bare sump where water can flow in, over and around, the material is not much of an obstruction and does little harm. However, in a sand bed or in live rock an excess of detritus impedes advective flow and thereby diminishes the rate at which substances reach the bacteria. If allowed to continue and escalate, the end result is obvious as the bacteria become less and less efficient at processing/reducing/converting (ammonium, nitrite, nitrate, phosphate, etc.) and the top tier organisms begin to suffer due to water quality degradation.

Nowhere is this more apparent as in a Pico or Nano tank with the relatively large ratio of organisms to water volume. Typically, in nano tanks where the substrate is not disturbed (and the detritus is not removed), they will function properly for 8 months to 1-1/2 years before the system has some major issues resulting in many of the higher life forms in distress or dying or, quite often, a total system crash.

On the topic of substrate, I have found that it is virtually impossible to vacuum the life out of it. I vacuum my shallow 1" substrate frequently and deeply 2x/week with my water changes and in between I can still see worm tracks up against the glass.

I'd say you are wrong. I have a 29 gallon bio-cube over 4 years with a 6 to 8" sand bed. Figured I'd just throw that out there.

Edit: I should clarify. I actually have two 29 gallon bio-cubes both over 4 But more to the point I feel you are making a blanket statement. Check the any of the boards here and you will read about tank crashes which happen for many reasons. I wouldn't be so swift to put a time stamp on a issues, distress, death, decay, or a total crash because someone has undisturbed bed. You don't have the data to back up that statement.

 

[Nano sapiens]

I'd say you are wrong. I have a 29 gallon bio-cube over 4 years with a 6 to 8" sand bed. Figured I'd just throw that out there.

Edit: I should clarify. I actually have two 29 gallon bio-cubes both over 4 But more to the point I feel you are making a blanket statement. Check the any of the boards here and you will read about tank crashes which happen for many reasons. I wouldn't be so swift to put a time stamp on a issues, distress, death, decay, or a total crash because someone has undisturbed bed. You don't have the data to back up that statement.

You are correct that nano tanks can fail for a variety of reasons, but what I am referring to here are those that don't have any equipment failures, power outages, etc., but still experience all manner of problems unrelated to equipment or aquarist ignorance, incompetence or laziness. To clarify, I am referring to the much more typical pico and nano setups with shallow 1-2 inch sand beds, either sumpless or with small sumps with limited water volume, not a DSB nano which is more rare and often has a good sized sump attached. Does your tank have a sump with extra water volume? If so, is it really a 'nano' or just a smallish tank with a larger water volume?

You should also note the word I used 'typically'. There are always exceptions to every rule and each pico or small tank's bio load, feeding, water change schedule, etc. can be very different which can have a very real effect on a pico or small nano tank's longevity in the context discussed.

I stand by my statement that a good majority of your 'typical' pico and small nano tanks, where the sand bed is left totally undisturbed and detritus is never removed by any means, experience difficulties (algae, cyano, poor coral health, disease and death of specimens, etc.) and some experience total meltdowns before 1 - 1/2 years.

Back on the topic of this thread, DSBs, you do bring up an interesting point of whether nano tanks can benefit. It's working for you and I am glad to see that. Do you plan on running the tank for a few more years?

 

[saf1]

You are correct that nano tanks can fail for a variety of reasons, but what I am referring to here are those that don't have any equipment failures, power outages, etc., but still experience all manner of problems unrelated to equipment or aquarist ignorance, incompetence or laziness. To clarify, I am referring to the much more typical pico and nano setups with shallow 1-2 inch sand beds, either sumpless or with small sumps with limited water volume, not a DSB nano which is more rare and often has a good sized sump attached. Does your tank have a sump with extra water volume? If so, is it really a 'nano' or just a smallish tank with a larger water volume?

You should also note the word I used 'typically'. There are always exceptions to every rule and each pico or small tank's bio load, feeding, water change schedule, etc. can be very different which can have a very real effect on a pico or small nano tank's longevity in the context discussed.

I stand by my statement that a good majority of your 'typical' pico and small nano tanks, where the sand bed is left totally undisturbed and detritus is never removed by any means, experience difficulties (algae, cyano, poor coral health, disease and death of specimens, etc.) and some experience total meltdowns before 1 - 1/2 years.

Back on the topic of this thread, DSBs, you do bring up an interesting point of whether nano tanks can benefit. It's working for you and I am glad to see that. Do you plan on running the tank for a few more years?

No sump. It is a 29 gallon Oceanic Bio Cube.

I will run it for has long has I am in the hobby. I don't know where the nano pico small medium or large fall but I consider it a nano. The plan it to merge them together into a 40 breeder. Deep sand live rock corals fish etc. I also don't run a skimmer and do has few water changes has possible. I believe to keep it simple.

I guess what I am saying is that size doesn't dictate success in this hobby when we have all read posts on this board about failures. I would agree with your comment about total water volume and what it can do but those tanks still fail.

only other thing of note is I keep corals that like my water type which are soft and a few LPS.

 

[elegance coral]

Based on this conversation, I'm assuming the benthic sand bed critters are the "not your must have organisms". In this case, you are making an incorrect assumption about extra nutrients being added to support them. Those "not your must have organisms" are existing the same nutrients being added to feed the "must have organisms", aka the fish and the corals. It's not a matter of adding yet more, but simply the sand bed critters (I'm including everything from the bacteria on up) taking up the nutrients that result from the inevitable feeding of the tank. There are no extra source of nutrients just because of having a sand bed and associated critters. While there is certainly P bound up in those organisms, it is bound up in them and unavailable until they are consumed by something else, and so on and so forth. As unavailable and bound up, they totally irrelevant in terms of contributing to the P that can cause issues in our tanks...in fact, they help by taking up the P and removing it from the water column, giving us more time to deal with ultimate removal by whatever means you like.

How's it going Bill?

I've been reading along, but don't have much time to post. Gotta touch on a couple of things here though.

"they totally irrelevant in terms of contributing to the P that can cause issues in our tanks"
Not exactly true. They are irrelevant to the total P content of our glass boxes, but they are a major contributor to the "P that can cause issues in our tanks". They take organically bound P, which is harmless, and convert it into inorganic P, which causes issues in our tanks. They do the same with other elements that could potentially cause issues in our tanks, like heavy metals. The more of these types of critters we have, the more inorganic P they're producing.

"in fact, they help by taking up the P and removing it from the water column, giving us more time to deal with ultimate removal by whatever means you like."

They are adding P to the water column. Not "removing it from the water column". These are reducers/composers. They take solid organic particles from the sand and dissolve it as it passes through their digestive systems. They take the solid food we feed, break it down, and release the elements it contained (like P) into our water.

"It's not a matter of adding yet more, but simply the sand bed critters (I'm including everything from the bacteria on up) taking up the nutrients that result from the inevitable feeding of the tank."

I'm not saying you're implying anything here, but many people read statements like this and get the wrong idea. From statements like this it sounds as though these critters are "taking up the nutrients", and somehow through this process, reducing the harmful substances of the system. They aren't. At least not in a mature and stable system. It's been driven into the minds of hobbyists that as these critters grow and reproduce, they take up nutrients from the system, incorporate them into their tissues, and help to reduce nutrient levels in our water. This isn't true. It is irrelevant what one organism is doing. What's important is what the population as a whole is doing. As one organism is growing and reproducing, others are dying. In a relatively stable system, these populations will remain relatively stable, and there will be no reduction of free nutrients in the system. The only way to see any benefit from this process would be to have a continually growing population. The only way to have a continually growing population is to have a continually growing supply of rotting organic matter in the tank to fuel this growth. You're never going to get ahead. You're never going to see any benefit due to the fact that these individuals incorporate nutrients into their tissues as they grow and reproduce, because there will always be others dying and releasing their bound nutrients back into the environment.

 

[GroktheCube]

Main reason I went BB was so that I could push more flow.

That said, my sand bed seemed pretty gross when I removed it at less than a year old.

I should say, it LOOKED (dark brown) and SMELLED (mostly mercaptin odors, a little H2S, some unidentifiable "eww"). Whether that means it was harmful I cannot say.

Enough people have old tanks with DSBs that I don't think they're always detrimental. I've also heard plenty of crashes attributed to them, but perhaps those same tanks would have crashed with an SSB or as BB.

 

[saf1]

I've also heard plenty of crashes attributed to them, but perhaps those same tanks would have crashed with an SSB or as BB.

While all the technical jawing going about P this and P that the bottom line is that no one on this forum can say a tank will crash because they have a deep sand bed no more can they say a tank won't using a bare bottom. There just isn't enough factual information to support it.

If there was then everyone in this hobby would be running the exact same setups to prevent many of the tank crashing or poor coral / fish health threads. For every DSB post there are probably an equal number of bare or other form of gravel. Lighting, filters, chemicals, hands in, hands out, lighting type, or enter whatever personal bias you/I have. We have all ready them, felt sorry, or tried to help (maybe even experienced it in our hobby time).

The onus is on the hobbyist and there isn't one form factor for success...we each have our own.

 

[Randy Holmes-Farley]

the point is that it is time delayed. more is coming in faster than it can get out. organisms are always expelling waste. the tank is getting fed faster than all of the poo can go away, the greater the amount of animals the longer it takes for the P to get converted. sequestering is still not exporting. i thought i made that clear several pages back. recycling is not exporting. if more is coming in, and there are more biomass, there must be more poo for the organisms to eat. keeping poo as a pet in order to feed these other organisms. which in turn supply more poo.
G~

I just don't see the point of that paragraph.

Sure, the release of inorganic phosphate from metabolized organic matter, whether dissolved or in solid feces that may partly enter the substrate, will be slower than release of inorganic phosphate directly by organism excretion.

Who cares? if you have adequate export means to deal with ALL of the P added, it makes no difference if some takes a short or very long time to eventually be released as inorganic P.

I can handle it. I do not really care what route it takes from the fish anus to my trash can (GFO and GAC) or drain (skimmate and water changes) or backyard (harvested macroalgae) or into more creature tissue mass. It goes some route and my creatures are happy. So I am happy.

 

[elegance coral]

While all the technical jawing going about P this and P that the bottom line is that no one on this forum can say a tank will crash because they have a deep sand bed no more can they say a tank won't using a bare bottom. There just isn't enough factual information to support it.

If there was then everyone in this hobby would be running the exact same setups to prevent many of the tank crashing or poor coral / fish health threads. For every DSB post there are probably an equal number of bare or other form of gravel. Lighting, filters, chemicals, hands in, hands out, lighting type, or enter whatever personal bias you/I have. We have all ready them, felt sorry, or tried to help (maybe even experienced it in our hobby time).

The onus is on the hobbyist and there isn't one form factor for success...we each have our own.

We can describe through science (biology and chemistry) how a DSB may lead to tank crashes. We can not describe how a clean glass bottom would lead to a tank crash. There is no scientific explanation to link a clean glass bottom with a tank crash.

Like Randy keeps pointing out, there are ways to offset the negative effects of a DSB. (GFO, GAC, skimming, water changes...........) so you can have a successful tank with a DSB. The fact that someone may have a seemingly successful system with a DSB is not evidence that the DSB is beneficial, or that it isn't having a negative impact on the system.

 

[elegance coral]

Who cares? if you have adequate export means to deal with ALL of the P added, it makes no difference if some takes a short or very long time to eventually be released as inorganic P.

It makes a huge difference. If we add food/phosphate, and remove it quickly, the overall phosphate content of the system remains relatively low. The longer it takes for us to remove that phosphate, the higher the overall phosphate content of the system becomes. We're simply storing phosphate in the system until its eventual exportation.

Phosphate can be cycled very tightly. Moving from organic to inorganic and back many times before it's eventually released into the open water as inorganic phosphate and removed by the means you describe. This tight cycling can fuel unwanted organisms like algae, and hinder the growth of wanted organisms like stony corals, even when our test kits are telling us we're maintaining a very low inorganic phosphate level.

If we have an abundance of rotting organic matter in our sediments (rock and sand) the phosphate being released can be utilized by algae growing on those sediments. When that algae dies, (if its eaten by snails or not), it returns to the sediments as more rotting organic matter to fuel more algae growth. This process can be repeated many, many times. None of this phosphate will be detected by our test kits, or be removed through filtration like GFO, but it does have the ability to effect the corals that we try to grow on these same sediments.

 

[rounder45]

setup the system to export detritus as fast as possible. bigger skimmers. true settling tanks that are cleaned regularly.

do you have a reference to your "solution" that has proven longevity? What is a "big" skimmer?... most folk have found too Big a skimmer and little to no waste is exported.... settling tanks... ok... what is a settling tank and who has been using one for years and proven this is a better solution than those that have actually been maintaining their aquarium for a long duration?

 

[Amphiprionocellaris]

It makes a huge difference. If we add food/phosphate, and remove it quickly, the overall phosphate content of the system remains relatively low. The longer it takes for us to remove that phosphate, the higher the overall phosphate content of the system becomes. We're simply storing phosphate in the system until its eventual exportation.

Assuming there is a major imbalance between the input and output. Incorporation into growth is so inefficient that it probably represents a fairly small sequestration once the system is mature. So again, even if a particular molecule takes a while to move through the pool, that doesn't necessarily mean the pool is increasing if the net import is still 0 (ie. is coupled with aggressive export). Of course, the pool in a healthy tank is increasing due to the growth of everything in the tank, but that doesn't represent the sort of "ticking time bomb" buildup that is often cited as a problem with DSBs, unless the population in the tank collapses (and that principle holds true with or without a sand bed. I would also argue that one of the biggest benefits of a sand bed with fauna (not a depopulated one) is that they rapidly speed up the cycling of phosphorus in the sand bed and removal from it into forms that are more easily removed via filtration. So they switch the system from one of storage (which a depopulated bed could represent, because such beds have very slow remineralization rates compared to a populated one) to one of removal from the sand bed. I think a decline and collapse of said population is also one of the biggest factors (though this is speculation) in a system crash.

Phosphate can be cycled very tightly. Moving from organic to inorganic and back many times before it's eventually released into the open water as inorganic phosphate and removed by the means you describe. This tight cycling can fuel unwanted organisms like algae, and hinder the growth of wanted organisms like stony corals, even when our test kits are telling us we're maintaining a very low inorganic phosphate level.

If we have an abundance of rotting organic matter in our sediments (rock and sand) the phosphate being released can be utilized by algae growing on those sediments. When that algae dies, (if its eaten by snails or not), it returns to the sediments as more rotting organic matter to fuel more algae growth. This process can be repeated many, many times. None of this phosphate will be detected by our test kits, or be removed through filtration like GFO, but it does have the ability to effect the corals that we try to grow on these same sediments.

But what about using this cycling for naturally meeting the phosphate demands of the organisms we want? Some people, myself included, use sand beds specifically to get the tight recycling that the benthos provides, with resins, GFO, and skimming to remove the soluble phosphate that is not taken up immediately, and a healthy population of herbivores to control any algae growth that occurs; that's my way of simulating as best I can the natural dynamic on the reef. Corals (along with lots of other organisms in the tank, but it's safe to say we mostly focus on corals) need that nutrient flow to survive and grow, and there's evidence in the primary literature that one of the important sources for them is recycled organic detritus. Of course, that's not the only way to get the necessary nutrients to the corals, but for someone like me who doesn't regularly have predictable free time, the sand bed can provide a great "autopilot" in that regard (not to mention the role that the macrofaunal population itself can play, via e.g. egg and larval production, etc.).

What matters most in nature as far as algae vs. coral dominance is the SRP, not total organic pool or how much is being recycled through at any particular moment, just the standing pool of SRP, which is one of the biggest components our tests do measure. That's why I've repeatedly been making the point that if you have aggressive export that keeps that pool from getting large, even with rapid P flow from whatever source, the system will be healthy. I also have one data point to back that up.

Yes, I am cheekily referring to my own tank as a data point...

 

[Reefin' Dude]

"More is coming in faster than it can get out". Baseless statement with zero evidence behind it. Not true in a properly established tank.

"The tank is getting fed faster than all of the poo can go away" Another baseless statement with zero evidence.

Randy did in Post #474 he also provided us with the amount of P released by fish in the solid form. is this wrong? organic material does not just spontaneously decompose. all i am saying is that in order for there to be a lowering of total P in a system, then all of the P released by an organism, must be removed before that organisms produces more waste material which contains P.

"The greater amount of poo the the longer it takes for the P to get converted". Simply not true because the higher load of animals that supposedly leads to that poo also processes it more quickly.

it is still in the system and still able to be utilized. a total increase in P of the system. those same organisms that lead to a faster processing of P are adding more P to the system also. it just doesn't disappear.

No one said sequestration is exporting. But coral growth is a form of sequestration, so if you're going to argue that sequestration is a bad thing, better ditch your corals.

corals are your must have organisms. yes, they are sequestering P. that P is in a form that makes sense to the system you are keeping. i am saying that all of the benthic organisms in the system are not helping to keep the total P of the system stable. they are increasing the total P of the entire system. every organisms is going to contain P, but it is also going to need P.

No one said recycling is exporting. Recycling returns nutrients including phosphorus back into the water column so that they CAN get exported. The system will increase in biomass over time if it is healthy; if it is not increasing, it is not healthy. I don't understand why growth of an ecosystem is a bad thing, and you should probably let the whole of ecology know about that one, too.

it is bad in a system that is of a finite size. a container can only handle a certain sized population of any organism. it can only contain enough resources for a certain maximum population. i am pretty sure the ecology knows this.

No more "poo" can be running through the system than is input. Done. End of story. If there is more biomass recycling that "poo", so what? What matters to corals are soluble reactive phosphates (SRP, which is what a P test actually measures). The goal is to balance the input with the export, and that's exactly why we use resins, GFOs, algal turf scrubbers, and on down the line.

how can this be true? this can only be true if all of feces/dead decomposes spontaneously once it leaves the organisms. this can not be true because then the benthic organisms would not have anything to eat. as long as there is P being released through the decomposition of feces/dead while more P is being produced by organisms dying and pooing, then there is going to be an increase in waste organic material if more food is going into the system. the only way this is not going to be true is if the system is 100% efficient and no food is entering the system.

This statement leads me to believe you didn't understand the point of the keg analogy at all. I wasn't discussing where the resources come from (but that would be food in this scenario), I was illustrating that if your input matches your output, the total pool will not change regardless of how big the pool is and how long it takes something to travel through the pool. You argue that because it takes time for all of a particular input to be removed, it must be increasing, but I wanted to illustrate that in reality it doesn't matter how long it takes if the input/output is balanced. That's a basic concept of food webs and ecology. Though you are right that an increasing population does indeed require resources, again another basic concept of ecology. But that has nothing to do with net import, flux balancing, and steady states.

i get what you were trying to get at, but again you are missing the rate of decomposition of the dead/feces. it will not be balanced if there is an increase in population of the waste organic material feeding organisms. they are showing that there is not a balance.

I'm starting to get lost here, because there are a bunch of distantly related concepts being thrown out here. Yes, growth is a sequestration, so growth is required to sequester something. And yes, if it's not being sequestered, then it's available for removal. The resources you mention for removal are ones we already use, again the resins, GFO, and skimming. That's part of designing a system for export. Again, these statements are all mostly true, but so what? Why, specifically, does it matter if more soluble reactive phosphate is produced to be removed by our filtration mechanisms instead of being sequestered in new growth?

the ones listed are all going after the iP that is in the water column. they all must wait for the oP to become iP before they can do their job. i am just suggesting that we should siphon out the waste organic material before it has a chance to decompose. moving the processes closer to the spontaneous decomposition scale. removing the waste organic material when it is in the 37% state or less depending on its rate of decomposition. trying to get this oP out to keep the amount of decomposition down.

As far as the overdosing of carbon, it would lead to a decrease in the oxygen penetration depth, increased CO2 production, and increased rates of denitrification, and possibly sulfide production if it's way overdosed. But that's a completely different topic regardless.

no, it is showing that resources are not unlimited for all of the organisms in the system. trading O2 for CO2. i for one would rather have more O2 in the system, then CO2.

Steady state, by definition, is a state whereby the population is not changing. If you feed the same amount, and keep your resins and GFO's properly replaced, then steady state will be reached at the point where the population reaches its carrying capacity based on the standing pool of SRP (which will likely be low). Hopefully, while feeding, you also have nutrient export mechanisms in place; otherwise you're going to see an increase in the pool size, and should probably run some sort of filtration to enhance export.

the corals are not growing, and the benthic organisms are not growing. a 100% recycled system with respect to P. again, this is only going to occur if there is spontaneous decomposition of feces/dead where the organisms are not dying/producing more feces by the time the previous feces/dead have decomposed.

No the "must have organism" doesn't care how it gets what it needs. But doing all of that (recycling, processing, export, etc, as opposed to direct removal before it can enter the food chain) IS NOT harmful to the tank, as you imply. So to follow the analogy (which I now hesitate to do, because I have a feeling it's not going to emerge in the same way as I wrote it), you don't need to homebrew your beer, but some people like to, and they should know the details of it and that it's no worse than buying your beer premade. And personally, I prefer to have my system set up in such a way that the whole system deals with most of it and I only have to intervene occasionally for water changes and dosing.

as long as the food chain is not causing a change in amount of iP available in the water column. for those running system that require very low soluble iNutrients, then yes, the food chain will be detrimental to the health of the system because they are part of the production of iNutrients back into the water column. if one is keeping a system that requires soluble iNutrients, then you are absolutely right and they are not going to harm the system, and in fact will help the system maintain the correct levels of soluble iNutrients.

I did not once ever say that a sand bed is necessary or the only way to e.g. keep a healthy coral.

neither have I. i am just saying to match the methodology to the must have organisms one is trying to keep.

Please re read all of the posts on this because I don't really have the inclination at this point to re-type everything I've explained, because I'm not convinced it's been effective. But I'll at least give a basic rundown. The sand bed as a whole processes and recycles the organic matter that comes to it, leading both to nutrients flowing up the food chain and being broken down into soluble components that can then be removed. The "poo", does not stay around long; it is processed very quickly, and re enters the food chain as nutrients necessary for growth. This is all balanced by removal of especially the SRP, so that in a mature system, all input is removed with the exception of the small percentage that is used to support new biomass.

it is not being process as fast as the organism is producing more poo. post #474 told us that. it takes 24 hours for all but 37% of the P to become iP. that leaves 37% more needing to get converted to iP. even if it is a half life, that is days before all of that 37% has been converted to iP. unless that fish does not poo by the time all of the 37% has been converted, there is going to be a total increase in P capable of becoming iP.

Because over time, the bacterial and macrofaunal populations reach their respective carrying capacities and equilibria. That takes time to happen, and it will happen regardless of how you set your tank up unless it consists of a glass box with corals and fish only. At that point of maturity, the change will be minimal, but up to then, the dynamics are stabilizing and populations are reaching maturity, and so the energy and nutrient budgets are continually shifting (towards the equilibrium values) until stability is reached.

what is limiting their carrying capacity? is it space or nutrients? i propose that it is space.

It reaches equilibrium when the input matches the output, which has absolutely nothing to do with the pool size (ie. the sediment being "full"). It can absolutely accept more with a concurrent change in population size as the carrying capacity changes. That's how an ecological equilibrium works.

or they run out of space. space is resource. we must look at all resources needed by an organism.

Post #479 and Post #497 are good examples.

Not disagreeing you can do that if you want. It won't cause harm unless you rely on the benthic macrofaunal community for denitrification.

agree. just match the methodology to the must have organism. don't fight nature, work with it. we need to stop thinking that one setup can work for all organisms.

Nope.

That's my whole point. It does NOT need to be done for the sand bed to remain functioning. The movement of material is provided by the natural recycling of elements that takes place, with removal being balanced by fresh input from the aquarist. You absolutely do NOT need to "cull the herd" with the benthos. It reaches a carrying capacity and stays there unless the supply of nutrients is diminished through lack of feeding or suddenly new filtration.

back to Post #479 and Post #497. living space is a resource. a growing population is a healthy population.

Or let the benthos do its thing and use resins, GFO, skimming, etc remove the excess SRP. This is one of my big problems: the approach you advocate is not a blanket approach, it's not suitable for everyone, and it's not the only way to go about having a healthy reef.

just match the methodology to the must have organism, or to the aquarist available resources. if one has the money for all of this equipment and material, then yes, go for it, but they are not necessary to the extent that they are promoted in this hobby. the waste organic material eventually needs to come out. you can either remove it in small batches regularly, or you can hide it in a substrate and then remove it later when the resources needed to cover up the affects of the iNutrients being released by the waste organic material decomposing in the substrate become to resource dependent to be viable.

My regime: Weekly water changes of 10%, purigen and carbon, skimming, a healthy sand bed, ridiculous amounts of plankton and pellet food feeding, and I have never once detected nitrate or phosphate. I bet you could poll 100 different aquarists and get 100 different maintenance regimes, and I'd bet that the majority of them are very successful.

yep, absolutely. i have not denied there are many different ways to keep a successful reef tank. it is about matching the resources to the must have organisms and the type of maintenance the aquarist is capable of sustaining.

Based on this conversation, I'm assuming the benthic sand bed critters are the "not your must have organisms". In this case, you are making an incorrect assumption about extra nutrients being added to support them. Those "not your must have organisms" are existing the same nutrients being added to feed the "must have organisms", aka the fish and the corals. It's not a matter of adding yet more, but simply the sand bed critters (I'm including everything from the bacteria on up) taking up the nutrients that result from the inevitable feeding of the tank. There are no extra source of nutrients just because of having a sand bed and associated critters. While there is certainly P bound up in those organisms, it is bound up in them and unavailable until they are consumed by something else, and so on and so forth. As unavailable and bound up, they totally irrelevant in terms of contributing to the P that can cause issues in our tanks...in fact, they help by taking up the P and removing it from the water column, giving us more time to deal with ultimate removal by whatever means you like.

Agreeish. the points i was making earlier in this post about the rate of decomposition being slower than the rate of death/excretion of the organisms with respect to the food coming in. this is going to lead to an increase in waste organic material in the system.

I think this is a super, super important point, and I'm glad you brought it up, because that's one of the big open-ended questions: how quickly does it take the sediment to clog? This is something that (I bet anyone who's been following this thread can predict my next words...) we simply don't know yet, and it really is something hugely important that advocates of sand bed methodologies (such as myself) need to address. I would argue based on my experience that clogging doesn't take place over the tens of years our aquaria run, based on my experience (but again, the plural of anecdote is not data), but this is honestly something that really requires more study. I think you bring to the table some very important examples with nano and pico aquaria, because those are going to experience the same-magnitude process rates, but the percentage impact will be much larger. Aquarists who are keeping those systems must honestly be very careful to consider the import-export rates of major nutrients, because even a slight imbalance over even small time scales will have a huge impact.

If permeability changes through the accumulation of small particles, then as you say, advective flow could be dramatically decreased, which would then decrease the ability of the benthic community to do the nutrient processing we use it for. This could be one source of the old tank syndrome, and also one reason mature tanks start to unexpectedly see algae growth. In a diffusion-dominated environment (and it is really open-ended how we should consider our systems; and it's possible that it's entirely situation-dependent), this is less the case, because permeability does not play a role in diffusion. At the same time, some organisms responsible for advection actually demonstrate the ability to respond to and even alter the permeability of their domain by moving such small particles to be removed by mechanical export! How much that occurs in the aquarium is of course anyone's guess (and it really is a guess until we secure a source of funding for actual aquarium science), but this whole topic is hugely important and really needs more investigation. I am a staunch proponent of sand bed methodologies as one way to lead to a successful reef tank, but I will absolutely and completely say that sediment clogging is one major open question we need to address as support for our method(s). And this idea has so many unknown aspects to it that the questions and ideas for experimentation grow almost exponentially!!!

Please pardon my wild speculation and exuberance on this topic, and I apologize if I throw concepts and terms out without proper explanation; this particular subject is what I've been studying for my PhD and so ideas and hypotheses can proliferate wildly when I talk about them! (but on that note, to anyone observing this thread, please ask if we throw out unfamiliar concepts or terms...the reason RC exists is first and foremost to educate). These sorts of unanswered questions are where the real scientific and hobby progress happens!

Agree.

if material is accumulating, it really doesn't matter what it is, it needs to be addressed. it is a sign that a system is gaining mass and can not be sustained. it could be in minutes, hours, years, or decades. no system can increase in mass indefinitely and maintain a stable state.

G~

 

[Amphiprionocellaris]

Randy did in Post #474 he also provided us with the amount of P released by fish in the solid form. is this wrong? organic material does not just spontaneously decompose. all i am saying is that in order for there to be a lowering of total P in a system, then all of the P released by an organism, must be removed before that organisms produces more waste material which contains P.

It does not spontaneously decompose, no, but my point is that in a healthy, fully functioning tank at maturity, there is a mass balance such that even if it takes time to decompose, the NET results are independent. Take the example I have in the picture (I made the numbers up for simplicity, but the 50 nmol/d moving from the detritus to the SRP is based on the article Randy linked). Based on a system at steady state, assuming again that sufficient SRP removal is in place so that removal is limited by SRP present (ie. there is excess removal potential), the system is balanced because what is going into each pool is balanced by what is leaving. It does not matter if the matter leaving e.g. the sand bed has been there for five days or twenty, because the fresh input is balanced by removal of old material, and the whole system is balanced in terms of input and output. I think the disconnect here is looking at one organism when I'm looking at the whole community.

Now of course, the system is not strictly speaking at steady state, because our organisms - especially corals - are growing, and so there might be a ~10% or so arrow leading from SRP to corals. You could also add some algae growth and removal via herbivores, which would be another set of bubbles, but again, by definition at steady state, all of these are balanced because what matters is input/output rates, not residence time (how long a particular particle stays in a single pool). Of course, this only applies to mature systems where steady state is a reasonable approximation.

it is still in the system and still able to be utilized. a total increase in P of the system. those same organisms that lead to a faster processing of P are adding more P to the system also. it just doesn't disappear.

Again, this assumes that the population is growing. In my systems, once established, I don't usually see marked growth of the benthic community, because their carrying capacity is usually reached within the first year. If anything, I see a small decline over the next year or so after that as the large stored pools from my uncooked rock are removed.

corals are your must have organisms. yes, they are sequestering P. that P is in a form that makes sense to the system you are keeping. i am saying that all of the benthic organisms in the system are not helping to keep the total P of the system stable. they are increasing the total P of the entire system. every organisms is going to contain P, but it is also going to need P.

Again, at steady state, the pool size does not matter, the input/output rates do. The benthic organisms are only leading to an increase in total system P if that population is growing rather than at steady state. In my experience and in nature, most of the benthos is at steady state because these organisms have a rapid turnover and thus reach equilibrium much more quickly. They also increase the rate of detrital removal. Looking at my picture again, without the benthic infauna, the arrow leading from the sediment could be much smaller than the arrow leading in, in which case there's a very serious problem on your hands, and again one of the things I think leads to crashes.

it is bad in a system that is of a finite size. a container can only handle a certain sized population of any organism. it can only contain enough resources for a certain maximum population. i am pretty sure the ecology knows this.

What this ignores is carrying capacity. You are probably right that these things are spatially limited, but once they reach carrying capacity, the population stabilizes, which is not a bad thing.

how can this be true? this can only be true if all of feces/dead decomposes spontaneously once it leaves the organisms. this can not be true because then the benthic organisms would not have anything to eat. as long as there is P being released through the decomposition of feces/dead while more P is being produced by organisms dying and pooing, then there is going to be an increase in waste organic material if more food is going into the system. the only way this is not going to be true is if the system is 100% efficient and no food is entering the system.

Again, see the mass balance picture. Decomposition does not need to be spontaneous because residence time is not important compared to instantaneous rates.

i get what you were trying to get at, but again you are missing the rate of decomposition of the dead/feces. it will not be balanced if there is an increase in population of the waste organic material feeding organisms. they are showing that there is not a balance.

By strict definition our systems are not balanced, due at the very least to coral growth, so in many ways this point is somewhat academic and not entirely practical. Again, once the community reaches steady state, however, there is a balance, because there is not an increase in population.

the ones listed are all going after the iP that is in the water column. they all must wait for the oP to become iP before they can do their job. i am just suggesting that we should siphon out the waste organic material before it has a chance to decompose. moving the processes closer to the spontaneous decomposition scale. removing the waste organic material when it is in the 37% state or less depending on its rate of decomposition. trying to get this oP out to keep the amount of decomposition down.

This is true, but again it's not the only way to keep SRP down. And it's worth noting that times of highest oP production via fish waste coincides with the fastest rates of associated corals (via the paper Randy linked). You can get exactly the same results as far as SRP with a sand bed WITH fauna (a sand bed without, now that's a different story...)

no, it is showing that resources are not unlimited for all of the organisms in the system. trading O2 for CO2. i for one would rather have more O2 in the system, then CO2.

Carbon is essentially the global limiting element. I was simply explaining the exact effects one would expect if one added too much DOC, and it is indeed a bad thing. But to a limited extent, dosing more is a good thing because it does increase rates of nitrogen removal.

the corals are not growing, and the benthic organisms are not growing. a 100% recycled system with respect to P. again, this is only going to occur if there is spontaneous decomposition of feces/dead where the organisms are not dying/producing more feces by the time the previous feces/dead have decomposed.

Once again, residence time does not matter in a steady-state or near steady-state system.

as long as the food chain is not causing a change in amount of iP available in the water column. for those running system that require very low soluble iNutrients, then yes, the food chain will be detrimental to the health of the system because they are part of the production of iNutrients back into the water column. if one is keeping a system that requires soluble iNutrients, then you are absolutely right and they are not going to harm the system, and in fact will help the system maintain the correct levels of soluble iNutrients.

Couple things. First, corals do require SRP (and SRN, SRC, etc), so we can't really delineate between a system that needs it and a system that doesn't. All life needs it. What you are referring to is more the threshhold SRP (~1 ppm SRP) that determines algal vs coral dominance. And the very point of removal methods is to keep that pool down. The food chain does not necessarily add to SRP when those removal mechanisms are in place, because they tend to be very fast (because they are abiotic) relative to other biogenic rates. Pool size is independent of residence time at steady state, regardless of whether you have one arrow in and out vs. twenty.

it is not being process as fast as the organism is producing more poo. post #474 told us that. it takes 24 hours for all but 37% of the P to become iP. that leaves 37% more needing to get converted to iP. even if it is a half life, that is days before all of that 37% has been converted to iP. unless that fish does not poo by the time all of the 37% has been converted, there is going to be a total increase in P capable of becoming iP.

Steady state...though again of course this limits us to talking about mature systems. I think we have a disconnect because you're considering more an individual organism's or molecule's fate whereas I'm talking about emergent community properties that are the sum of all the processes going on.

what is limiting their carrying capacity? is it space or nutrients? i propose that it is space.

It depends on the amount of energy/nutrients flowing through the system; in a nutrient poor system, the carrying capacity is determined by nutrient rather than space availability. But regardless of what determines the carrying capacity, once it reaches the capacity, the population will stay there unless the total amount of resource is changed. If it is indeed space, then that's good news for us because then a tank has an intrinsic carrying capacity and we don't need to worry as much about sufficient energy flow to maintain the benthic community. In all honesty, given that most tanks have relatively low energy flow compared to natural benthos, I'd be willing to wager that it is nutrient supply to the sand bed that determines carrying capacity, not space except in small tanks.

or they run out of space. space is resource. we must look at all resources needed by an organism.

Basically what I said above; a system at carrying capacity does not have a net change. If the input and outputs were already balanced when that capacity was reached, they will remain balanced unless the aquarist increases the input rate (feeding). If indeed they are space-limited, which is more likely in nano and pico tanks than in "full size" tanks, that's something that gives inherent instability as one feeds more. Keep in mind that the types of organisms we're talking about, though, have natural densities of hundreds to thousands per square meter in nature.

agree. just match the methodology to the must have organism. don't fight nature, work with it. we need to stop thinking that one setup can work for all organisms.

I'd argue very strongly that sand beds are a great way to work with nature, if one understands what's going on in them and takes steps to ensure the benthic community remains healthy.

back to Post #479 and Post #497. living space is a resource. a growing population is a healthy population.

A steady population is also healthy. The only unhealthy population is a declining one.

just match the methodology to the must have organism, or to the aquarist available resources. if one has the money for all of this equipment and material, then yes, go for it, but they are not necessary to the extent that they are promoted in this hobby. the waste organic material eventually needs to come out. you can either remove it in small batches regularly, or you can hide it in a substrate and then remove it later when the resources needed to cover up the affects of the iNutrients being released by the waste organic material decomposing in the substrate become to resource dependent to be viable.

A healthy benthic population is key to keeping the waste organic material levels in the sediment low. With a healthy population, they remineralize organics with a higher than 99% efficiency, so a healthy sand bed does not hide nutrients. The tiny component that is not removed accumulates to significant portions over the course of decades.

yep, absolutely. i have not denied there are many different ways to keep a successful reef tank. it is about matching the resources to the must have organisms and the type of maintenance the aquarist is capable of sustaining.

Time is also a resource. Not everyone has the time to actively remove detritus on a daily basis. I can barely find time just to do weekly water changes, and if I were running without a healthy sand bed my tank would be in very dire straits.

if material is accumulating, it really doesn't matter what it is, it needs to be addressed. it is a sign that a system is gaining mass and can not be sustained. it could be in minutes, hours, years, or decades. no system can increase in mass indefinitely and maintain a stable state.

G~

I can go ahead and say that - unless there is something fundamentally different going on in the home aquarium - this material takes decades to accumulate in most cases to the point of affecting permeability. It is much faster in small tanks, of course, because the volume of sediment is smaller, so a semi-fixed rate of refractory material accumulation leads to a larger percent change.

 

[Paul B]

I still think your rugf system is worth a serious look . It has always interested me. Pushing water up through the substrate may be an improvement to diffusion advective flow and sand critters to move nutrients to the bacteria , now that we know we don't have to fret about denitrifying bacteria dying when exposed to oxygen..
I think the beer can is probably a bad idea though.

Tom don't push RUGFs. I like having the oldest tank on here especially with never having any problems. This thread is over 500 posts long. how many problem RUGF filter threads have you read? Have you ever heard of a RUGF failing? I think not.
My power has gone out for 4 or 5 days and my "benthic organisms" just laugh. It is a little annoying listening to all that laughing but they laugh even louder if something big like a manta ray dies in there.
My "benthic organisms" don't care if they are exposed to oxygen, laughing gas or Myley Cyrus "music", as nothing bothers them. They usually don't care if they are disturbed unless they are sleeping. But hey, there are a lot of expert DSB guys on here so have fun. :dance:

I would put a cool looking graph on here but I don't think there exists a RUGF graph.

References:
Me

 

[Amphiprionocellaris]

Tom don't push RUGFs. I like having the oldest tank on here especially with never having any problems. This thread is over 500 posts long. how many problem RUGF filter threads have you read? Have you ever heard of a RUGF failing? I think not.
My power has gone out for 4 or 5 days and my "benthic organisms" just laugh. It is a little annoying listening to all that laughing but they laugh even louder if something big like a manta ray dies in there.
My "benthic organisms" don't care if they are exposed to oxygen, laughing gas or Myley Cyrus "music", as nothing bothers them. They usually don't care if they are disturbed unless they are sleeping. But hey, there are a lot of expert DSB guys on here so have fun. :dance:

I would put a cool looking graph on here but I don't think there exists a RUGF graph.

References:
Me

Seriousness or not aside, that's the subject of lots of recent studies on denitrification in carbonate sand as a result of the type of advection an RUGF would generate (ie direct flow through the sediment). Turns out it's actually really effective regardless of whether you use artificial flow or biogenic flow (even if we're as a field undecided on WHY exactly it works...the main labs say it's because of formation of microniches within the carbonate particles themselves, but I'm not convinced because that would mean I have to rework the final chapter of my dissertation). My lab is working on using that principle on a massive scale for wastewater/eutrophication remediation, and I've got a little experimental tower running on a lab tank to see how much nitrate I can dump in and remove with it (so far, lots). I've even convinced my lab manager not to take my funding away, though whether that's from pity or accomplishment I can't say...