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

[Reefin' Dude]

Originally Posted by tmz
"cooking", purging, or curing LR utilize this process.

Mineralization or breakdown to refractory organics /aka sinking phosphate seem more likely, imo.
"Cooking" usually means leaving the rock in a darkened bin of water for a year or so .I think it may work as a result of bacterial degradation and mineralization ,sinking the phosphate and other elements in refractory organics or via mineralization. If it is a process that simply liberates the phosphate as you suggest via unidentified solubilizing bacteria with no export then where do you suppose the phosphate goes in the end?
it becomes the detritus you see at the bottom of the tank in which you are "cooking" the LR in. what else do you think that detritus is comprised of?

Sediment from mineralization and perhaps some refractory organics that sink the phosphate.

Why would there be a detritus degradation after a year? If there was why wouldn't the Pi just go back into the rock? In your unconnected dot the phosphate would just keep circulating back into the rock as some special unidentified solubilizing bacteria would break down the sediment.That just doesn't happen to a measureable extent .If it did what would be teh point of "cooking"?

it does go back into the calcium carbonate matrix. there is a constant give and take between the calcium carbonate structures and the bacteria. this creates a pull of P from the water column as long as the P is able to migrate downward. once the substrate is full of P, then the pull of P into substrate slows and stops. at this point is when we need to rely heavily on water borne ways of removing iP. the resins, the GFO, carbon dosing and using the skimmer to pull the bacteria out.

the point of "cooking" is to convert the iP bound to the calcium carbonate matrix into oP in the form of the bacterial bodies. at which point the oP can be removed by siphoning. how do you think "cooking" works?

G~

 

[tmz]

Personally, I advocate against disturbing a sand bed out of concern for the fauna themselves, given how important they are in my particular approach to reefing. I don't think anyone really knows what effect vacuuming would have on them, but I err on the side of caution. I think there's also something there about stirring up pockets of reduced substances which would then draw down oxygen levels, but that's also speculative until more research is done.

I don't stir deep beds either. Stirring stuff up and damaging fauna could be a concern. Shallow beds are support polycahetes, spaghetti worms ,bacteria ,pods et alia quite well,ime.

 

[tmz]

please look at how a sewage treatment plant operates because i have a feeling you feel that they also perform magic and are also able to make P vanish.

More dots. I've actually overseen the operation of several in the state institutions I ran during my career. Nothing vanishes but it can be sequestered.Conditiions in wastewater and sewage treatment are not like conditions in a reef tank and mostly irrelevant to this discussion,imo.

 

[tmz]

the point of "cooking" is to convert the iP bound to the calcium carbonate matrix into oP in the form of the bacterial bodies. at which point the oP can be removed by siphoning. how do you think "cooking" works?
Bacterial bodies degrade;ultimately there is no more energy to be had from degradation from the bacterial cascade . The phosphate is sunk at least for a very long time barring some extraordinary environmental change or activity by PSBs(phospahte solubilizing bacteria)which likely don't do much if anything in a reef tank),imo.
The only reason I mentioned PSBs is because you asserted a significant role for them several times but now say that's not what you meant.

 

[inetmug]

The worlds oceans,,,, are a DSB. Where I dive, you can dig and dig. It can not be all bad.

The detritus issue, which is why fine grain sand is used, is so it stays on top, where the CUC can get it. If you use the wrong stuff, you might have problems. You also need to keep the bed "charged" with Detritivores and the like. Here is a great article:

http://www.reefkeeping.com/issues/2002-03/rs/

My take is any issue with a DSB, after running one for 8+ years in a 55G with a sump, stems from lack of understanding of the system. Like a septic tank, it needs to be maintained with bacteria packs, or it stops working. So the DSB "recharge kits" are in order. Our oceans, do their own version of maintenance in the form of constant recharge, and surface movement. It just makes sense. Every once in awhile, like a hurricane, things get whacked out for awhile.

 

[saf1]

Cleaning sand beds or hands off.
I think the aversion to disturbing a bed comes from an early idea that the bacteria involved in dentrification would perish in the presence of oxygen that would disturb hypoxic areas where anaerobic activity was occurring and concern about disturbing pocketts of hydrogen sulfide. Maybe some worry about microfuana. The bacteria are faucltative.

Anecdotally , I do accept that leaving a bed undisturbed with a healthy population of sand fauna can work in some tanks as many report it does for long periods of time but I never got the effects I wanted that way and the choice of sand critters remains puzzling to me.

Personally, I've had good effects from puffing up and/or vacuuming the top inch or so of sand and leaving the deeper areas unstirred;not much gets down there anyway,ime. Never could understand why cleaning up the top was any different than employing sea cucumbers or other sand sifters in terms of sand bed disturbance.

I've had good success but then again I keep more softies than other coral types. I find it odd coming from strictly a diving perspective that the SPS corals many achieve look vastly different in natural environments and at depth. The skittle effect just isn't there.

More to the point regarding critters. I have a pair of Talbot damsels. For some reason one decided to dive bomb my hammer coral one night and dig a pretty deep cave. He or she used part of the hammer branch and a green star polyp bed. I couldn't figure out why they did it but they did. One sleeps in there. I guess my point is that the whole time digging or swooshing around he could bring out a bunch of stick looking things. Worms or whatever I guess their shell / encrusted stuff. In either case it was natural and I didn't have to stir anything.

I also have a bunch of clams from indo pacific sea farms that run amuck in the bed that I don't see. It isn't the cleanest of sand beds but it functions and has been up for over 3 years. Some of the original sand is over 11 years old... It may not be right for everyone nor do I recommend it, but it works for me. I just let nature takes its course.

 

[asylumdown]

if the system is wanting to be more eutrophic, then absolutely keep the benthic organisms, or if you really like them around. that is the your purpose. the problem i have is that all of these organisms are not doing anything to help maintain the trophic state of an oligotrophic system.

I feel a bit like :deadhorse1: saying this, but again we need to check ourselves with these nutrient terms. No coral reef, be that natural or captive, anywhere on planet earth, can exist in or as an 'oligotrophic system'. The best examples we have of true oligotrophic systems are various European and North American lakes (usually alpine). The only thing you find living in the most oligotrophic of them are mats of cyanobacteria, because "cyano" biofilms are in fact light, oxygen, and pH stratified assemblages of bacteria (cyano, hetero and autotrophic), diatoms, and dinoflagellates that together can fix nitrogen directly from the atmosphere while recycling the critically low number of carbon and phosphorous atoms they capture pretty much in perpetuity. Nothing else can live in them. No fish, no plants, and certainly not coral reefs in marine examples. Trophic state (i.e. eutrophic or oligotrophic) refers to either the amount of primary productivity occurring in that system, or by another definition the total weight of biomass in a given body of water. Coral reefs (including all the stony acroporid and montiporid reefs we love) are some of the most nutrient dense, high biomass places on the planet, with very high primary productivity, which by definition makes them highly eutrophic systems. Those nutrients just aren't in the water. Having low total dissolved nutrients in the water around the most productive ecosystem that's ever existed in the history of life is not a sign of oligotrophy. It is a sign of highly efficient capture and recycling pathways and a tremendous amount of biological activity.

There is mountains of published research on this. You are using the terms wrong, which I think is leading you to mis-apply the concepts as well.

Yes, you can remove a sand bed and technically reduce the 'trophic state' of your tank because you've physically removed biomass, but why would that have anything to do with the keeping of corals? What corals care about is the moment to moment chemistry of the water they are immersed in, not the total number of atoms bound up in the organisms and biological pathways around them. Everything else being equal, let's say a tank with a sand bed has 3 times the total biomass, and thus 3 times the total number of organic carbon, nitrogen and phosphate atoms relative to a bare bottom tank. However, if the bare bottom tank and the sand bed tank have the same levels of dissolved nitrate and phosphate in the water - which is easily testable and controllable via a myriad of available technologies - then from the coral's point of view there is no difference between those systems whatsoever.

As an analogy: the height of a dam and the size of the lake behind it doesn't necessarily have anything to with the downstream flow rate of the river. Running bare bottom to avoid accumulation of biomass and maintain a lower 'trophic' state is just lowering the height of the dam, but it's the flow rate of the river that we care about.

i want to clarify what i am suggesting about nutrient exports. i am not saying that detritus removal is the only way to remove P. i think that it should be made primary instead of tertiary. the way the marine hobby goes about P removal is more top down. i am just suggesting from the bottom up, that is all. i suggest using detritus removal by water changes as primary, with a heavy dose of skimming. if that is also not adequate then use resins, GFO, carbon dosing if needed. all of this is of course matched to the trophic state wishing to be emulated. adjust the skimming, the feeding, the siphoning, etc..... to maintain that particular trophic state. the way it is done now is the opposite. the only time detritus removal seems to be recommended is when the system has become so eutrophic that the only recourse is to start over. why does starting over help if it is not bringing the system back to as low of an initial P as possible?

G~

I would argue that by the time you see it as detritus, most of the P that it's going to contribute to your system's rocks, water, and organisms has already been contributed. Unless you're siting in front of your tank with the siphon waiting for your fish to poop, or you vacuum every bit of uneaten food 2 minutes after you feed it, the detritus you're seeing is the end result result of the process, not the beginning. If you call using GFO to remove dissolved orthophosphate from the water top down, then vacuuming the undecomposable fraction of organic matter that collects in overflows and sumps as detritus is like top-top down. That phosphate is already in play.

 

[asylumdown]

You pretty much summed up the focus of my dissertation in one paragraph, though I would argue that many of those are testable, just very difficult to do so in a controlled fashion in a fully functioning reef system with hundreds (if not more) of interactions happening simultaneously. A big part of what I do is computational/modeling work, which allows us to address that, but there's still a massive (hopefully, career-sustaining...) list of questions to address.

I can at least answer a few of those questions: the main maco organisms in the tank that matter in the sand bed are amphipods, medusa/spaghetti worms, various polychaetes especially bristle worms. It appears from my and others' research that the two most important things in terms of nutrient cycling are density of organisms and functional diversity (which is *perhaps* why multiple sand beds with different communities still do the same net processes). Perhaps surprisingly, hundreds of different combinations can yield the same results, and there is indeed community drift but it appears not to matter in terms of nitrogen cycling (I can only comment on N, because that's what my research is...it's probably similar for P); because the macro-organisms are more than anything facilitators and mediators for the microbes that actually do the stuff (and that are much more uniformly distributed), it makes sense that you can arrive at the same big picture through a variety of ways.

Of course that's just scratching the tip of the iceberg, and this is stuff that benthic ecology as a whole is just now starting to take into consideration in detail, and the past five years maybe have seen a massive shift in how we think of marine sediments. In many ways, the hobby has actually been out in front of mainstream science on this (given that the immediate stakes are a little higher for us). But as you said, we start adding layers and layers of variables whose effects we simply don't know, which is one reason (even if the funding were available, which is another story) it's really, really difficult to design direct empirical studies to test these things consistently. That said, we do have a framework of the general way things work, even if we're still filling in a lot of the details.

I know that still leaves a lot of questions open about the details of macrofauna in the sand bed, but we're at the edge of knowledge on that one.

You have my dream job. What PhD did you get, where, and what was your undergraduate and graduate work like? Also, where do you work? Sploosh.

And thanks for that, ask and ye shall receive I guess! When I said 'not-testable' I meant not testable by your average hobbyist for just the reasons you mentioned. I was lying in bed last night trying to think how you'd isolate all the competing variables that go in to substrate dynamics to test them and kept running up against the problem of interacting effects. To get reproducible results it seems like you'd have to simplify the system so much that you'd always have uncertainty in 'real world' husbandry recommendations.

Have you published any of your dissertation work? I'd looooove to read it. What metric did you evaluate N cycling against (efficiency, input/output, etc.)? How did you test the samples for nitrogen? Did you do mineralization or isotope analysis? Did you find that N accumulated anywhere in the sand bed that would have been an indication of long term problems? Did you measure total N or look at both total and inorganic? Any plans to look at phosphate next? I almost did a big phosphate analysis in my masters work on soils, but got scared away by the acids needed to test for total P, and the amount of time and effort needed to perform the sequential extractions to look at plant available fractions when I had 90 samples, no lab assistant, and 6 other variables to test for.

 

[Amphiprionocellaris]

You have my dream job. What PhD did you get, where, and what was your undergraduate and graduate work like? Also, where do you work? Sploosh.

There are some days when the numbers aren't cooperating that we'd disagree xD I'm currently finishing up (last year, hopefully) the PhD (in Marine Sciences) at the University of Georgia, though I got an undergrad in Biology form Hendrix College in Arkansas. Most of my stuff is actually focused on computer modeling of the whole complex system; I actually have a sister lab that does most of the empirical work and I do the data analysis and framework development. Which is nice when the numbers work out...but nature has a tendency to be less than cooperative.

And thanks for that, ask and ye shall receive I guess! When I said 'not-testable' I meant not testable by your average hobbyist for just the reasons you mentioned. I was lying in bed last night trying to think how you'd isolate all the competing variables that go in to substrate dynamics to test them and kept running up against the problem of interacting effects. To get reproducible results it seems like you'd have to simplify the system so much that you'd always have uncertainty in 'real world' husbandry recommendations.

That's the real trouble with aquarium science; honestly there isn't really a great way around it without invoking a lot of models. Ecology as a whole has the exact same problem. On the one hand it makes the whole thing really fun, but also very frustrating especially when you start trying to link it to real-world applications like an aquarium. One of the beauties of the modeling approach I use is the ability to build and manipulate complex systems, but getting the empirical data (either to build or to verify) is and always will be the boogeyman in that equation.

Have you published any of your dissertation work? I'd looooove to read it. What metric did you evaluate N cycling against (efficiency, input/output, etc.)? How did you test the samples for nitrogen? Did you do mineralization or isotope analysis? Did you find that N accumulated anywhere in the sand bed that would have been an indication of long term problems? Did you measure total N or look at both total and inorganic? Any plans to look at phosphate next? I almost did a big phosphate analysis in my masters work on soils, but got scared away by the acids needed to test for total P, and the amount of time and effort needed to perform the sequential extractions to look at plant available fractions when I had 90 samples, no lab assistant, and 6 other variables to test for.

I've only got one part out here (that may be behind a paywall, unfortunately), though that one isn't as related to aquaria as the other two that I'm currently writing, which directly look at nitrogen cycling. In that, I use multiple measures...efficiency and total rates of denitrification, especially, of all the nitrogen pools (the model took about a year and a half just to formulate...). Most of the data I use is actually pulled from other labs and literature, so it represents a wide variety of sources including isotopic methods and direct flux measurements (via simply tracking the concentration in the water), though I can say in no system did reactive nitrogen accumulate; the marine environment is typically nitrogen limited, so it's almost invariably all used up except in extreme cases. As far as the phosphates, that's a direction I might take my stuff post-doctorate, but that's all contingent on finding funding etc.etc. I also write specifically for the aquarium hobby trying to take the body of research and link it, which are essentially massive literature reviews with some models, but I can hardly call that peer-reviewed.

 

[Fredfish]

...
no offense, but you really do not understand the basics of a biological system...

lol. There's more than a little irony in that statement. I think I'll take my imperfect understanding of the basics of a biological systems to the sidelines for a bit and watch you argue with the guys that do science for a living.

 

[billsreef]

and that is why biodiversity and ecosystem are fancy words for phosphate sinks (cesspool)

Seems I keep diving in cesspools, aka one of one of the most biodiverse ecosytems on the planet...yup, you guessed it, the reef The ability of that diverse ecosystem to recycle nutrients such that the water on the reef is so nutrient poor, all the while the total nutrient levels of the reef on the whole are incredably high is something that is quite fascinating. Equally fascinating is our ability to recreate those cesspools (err, reefs) as well as we do.

I'm wondering, next class I take out to the sea grass beds, should I say "welcome to the cesspool, now jump in and start running transects"

 

[Fredfish]

...

I'm wondering, next class I take out to the sea grass beds, should I say "welcome to the cesspool, now jump in and start running transects"

Damn. I'd love to do some dives in a sea grass cesspool. Colour me jealous.

 

[billsreef]

Damn. I'd love to do some dives in a sea grass cesspool. Colour me jealous.

I don't get to jump into that cesspool often enough. One problem with being the captain, I've got stay on board on the boat....

 

[Fredfish]

I don't get to jump into that cesspool often enough. One problem with being the captain, I've got stay on board on the boat....

We always desire that which we do not have. Enjoy the dives you have. I need to look into getting under water again. It's been too long.

 

[billsreef]

We always desire that which we do not have. Enjoy the dives you have. I need to look into getting under water again. It's been too long.

Yeah, it's a rough day to bring a boat load of students out on the bay...and get paid for it

Actually this past weekend the local aquarium club did a dive with the Coral Restoration Foundation. Good to get wet "recreationally" and be helping out the reef. Their nursery is in a sandy (cesspool) area in between reefs.

 

[asylumdown]

I'm wondering, next class I take out to the sea grass beds, should I say "welcome to the cesspool, now jump in and start running transects"

I'd just like to point out for the record that when you're running sea grass transects, the magic can wear off pretty darn fast. I did it once as a research assistant in Honduras after a field school 6 years ago. It sounded super glamorous and amazing before I did it. By the time I was done, they could have announced a mega-hotel that would strip the shore clean for clueless tourists, and I wouldn't have shed a single tear.

Mind you, it was in 8 feet of choppy water and we weren't using scuba equipment, so I may have let my general frustration, exhaustion, and oxygen deprivation cloud my memories of the experience...

In retrospect, if someone came to me and said "Adam, today you're going to spend 8 hours counting the blades of grass in a tiny plastic frame in a line along your front lawn. Oh, and someone is going to stand there while you do it kicking the frame every few seconds so that you have to start over at least 4 times per sample. Oh, also, you have to hold your breath while you're counting. And do jumping jacks", I would probably tell them where I wanted our lead researcher to go at the end of every day.

 

[asylumdown]

There are some days when the numbers aren't cooperating that we'd disagree xD I'm currently finishing up (last year, hopefully) the PhD (in Marine Sciences) at the University of Georgia, though I got an undergrad in Biology form Hendrix College in Arkansas. Most of my stuff is actually focused on computer modeling of the whole complex system; I actually have a sister lab that does most of the empirical work and I do the data analysis and framework development. Which is nice when the numbers work out...but nature has a tendency to be less than cooperative.

Tell me about it. I spent 4 out of 5 days in a deep dark hole of self pity this week because every single one of the soil parameters that I measured for part of my graduate studies failed Levene's test of equality of error variance for the two way ANOVAs I had based my entire statistical analysis around. Nature is like a 2 year old. You tell it it needs to fit certain assumptions for you to be able to analyze it properly, so it does the opposite.

Yah. Science.

It sounds to me like your sister lab has all the fun...

That's the real trouble with aquarium science; honestly there isn't really a great way around it without invoking a lot of models. Ecology as a whole has the exact same problem. On the one hand it makes the whole thing really fun, but also very frustrating especially when you start trying to link it to real-world applications like an aquarium. One of the beauties of the modeling approach I use is the ability to build and manipulate complex systems, but getting the empirical data (either to build or to verify) is and always will be the boogeyman in that equation.

Isn't it annoying how reality keeps messing up our our models?

I've only got one part out here (that may be behind a paywall, unfortunately), though that one isn't as related to aquaria as the other two that I'm currently writing, which directly look at nitrogen cycling. In that, I use multiple measures...efficiency and total rates of denitrification, especially, of all the nitrogen pools (the model took about a year and a half just to formulate...). Most of the data I use is actually pulled from other labs and literature, so it represents a wide variety of sources including isotopic methods and direct flux measurements (via simply tracking the concentration in the water), though I can say in no system did reactive nitrogen accumulate; the marine environment is typically nitrogen limited, so it's almost invariably all used up except in extreme cases. As far as the phosphates, that's a direction I might take my stuff post-doctorate, but that's all contingent on finding funding etc.etc. I also write specifically for the aquarium hobby trying to take the body of research and link it, which are essentially massive literature reviews with some models, but I can hardly call that peer-reviewed.

Thankfully I've still got unfettered access to science direct (all those publishing companies are the modern equivalent of social vampires if you ask me). Also, I squealed like a little girl when I saw the title, because not only do I already have that paper in my Endnote library, I've cited it in the draft of the paper I should be working on when I'm spending time commenting on fish tank forums... My masters is all about mammalian bioturbation in a stabilizing, glaciolacustrine sandhill ecosystem in Saskatchewan, so if it's got the keyword 'bioturbation' attached to it on Google Scholar, I've pretty much read it.

I cited your paper as an example of how bioturbation has ecologically relevant consequences on nutrient dynamics in a diverse range of habitats. If I can get off Reef Central, I'll have a draft of said paper to my supervisor before I go to bed tonight...

 

[billsreef]

I'd just like to point out for the record that when you're running sea grass transects, the magic can wear off pretty darn fast.

Why do you think I'm the captain I get to watch the manatees swim by, while the people in the water are oblivious to the mega fauna outside their transect :lol: For even more fun, being students, I get to laugh while they try and set up a transect line....using a corner of the boat to anchor the line, which of course keeps moving with every little change of wind and current :lol: Researchers I take pity on, keep throwing them off the boat only minutes after they get back aboard :lol:

You tell it it needs to fit certain assumptions for you to be able to analyze it properly, so it does the opposite.

When nature isn't fitting the assumptions you want it to fit, sometimes you need to sit back a figure out just what it does fit. An old boss of mine was quite good at that. Occasionally the best discovery isn't what you thought you were looking for, but what you found

If I can get off Reef Central, I'll have a draft of said paper to my supervisor before I go to bed tonight...

Success on that draft?

 

[Reefin' Dude]

please look at how a sewage treatment plant operates because i have a feeling you feel that they also perform magic and are also able to make P vanish.

More dots. I've actually overseen the operation of several in the state institutions I ran during my career. Nothing vanishes but it can be sequestered.Conditiions in wastewater and sewage treatment are not like conditions in a reef tank and mostly irrelevant to this discussion,imo.

how is this irrelevant? i hear it all of the time that "refugiums" and the DSB act like sewage treatment plants. which they do, but not in the way they are reported. they imply that it is a way to make nutrients just disappear. there is significant material exported from a sewage treatment plant. it is not sequestered at the sewage treatment plant, it is actually removed. sent to land fills or in some cases converted to fertilizers. the point is that the P is not just vanishing. even in a sewage treatment plant there is a waste product that needs to be exported from the system.

the point of "cooking" is to convert the iP bound to the calcium carbonate matrix into oP in the form of the bacterial bodies. at which point the oP can be removed by siphoning. how do you think "cooking" works?
Bacterial bodies degrade;ultimately there is no more energy to be had from degradation from the bacterial cascade . The phosphate is sunk at least for a very long time barring some extraordinary environmental change or activity by PSBs(phospahte solubilizing bacteria)which likely don't do much if anything in a reef tank),imo.
The only reason I mentioned PSBs is because you asserted a significant role for them several times but now say that's not what you meant.

why do you think that PSB's are not doing much work in a reef tank? "cooking" LR shows that they are doing a significant amount of work in the system. all of that detritus building up while cooking is a visual indication that iP is being pulled from the calcium carbonate matrix. we know the cooking is done when the detrital accumulation stops.

yes, the bacterial flock can degrade releasing iP back into the system if not removed. why it is important to remove detritus on a regular basis. the less substrate for this bacterial flock to hide, the more often one needs to remove it in order to maintain the desired trophic level. if there is no more energy to be had from degradation from the bacterial cascade, then how is this material not considered a P sink? at what point do the PSB's start doing their work in our systems, if not all of the time?

I feel a bit like :deadhorse1: saying this, but again we need to check ourselves with these nutrient terms. No coral reef, be that natural or captive, anywhere on planet earth, can exist in or as an 'oligotrophic system'. The best examples we have of true oligotrophic systems are various European and North American lakes (usually alpine). The only thing you find living in the most oligotrophic of them are mats of cyanobacteria, because "cyano" biofilms are in fact light, oxygen, and pH stratified assemblages of bacteria (cyano, hetero and autotrophic), diatoms, and dinoflagellates that together can fix nitrogen directly from the atmosphere while recycling the critically low number of carbon and phosphorous atoms they capture pretty much in perpetuity. Nothing else can live in them. No fish, no plants, and certainly not coral reefs in marine examples. Trophic state (i.e. eutrophic or oligotrophic) refers to either the amount of primary productivity occurring in that system, or by another definition the total weight of biomass in a given body of water. Coral reefs (including all the stony acroporid and montiporid reefs we love) are some of the most nutrient dense, high biomass places on the planet, with very high primary productivity, which by definition makes them highly eutrophic systems. Those nutrients just aren't in the water. Having low total dissolved nutrients in the water around the most productive ecosystem that's ever existed in the history of life is not a sign of oligotrophy. It is a sign of highly efficient capture and recycling pathways and a tremendous amount of biological activity.

There is mountains of published research on this. You are using the terms wrong, which I think is leading you to mis-apply the concepts as well.

agreed. i have been using the terms to denote the amount of dissolved inorganic nutrients available in the water column. i will be more specific from now on. it does lead to confusion.

Yes, you can remove a sand bed and technically reduce the 'trophic state' of your tank because you've physically removed biomass, but why would that have anything to do with the keeping of corals? What corals care about is the moment to moment chemistry of the water they are immersed in, not the total number of atoms bound up in the organisms and biological pathways around them. Everything else being equal, let's say a tank with a sand bed has 3 times the total biomass, and thus 3 times the total number of organic carbon, nitrogen and phosphate atoms relative to a bare bottom tank. However, if the bare bottom tank and the sand bed tank have the same levels of dissolved nitrate and phosphate in the water - which is easily testable and controllable via a myriad of available technologies - then from the coral's point of view there is no difference between those systems whatsoever.

you are correct. the point i am trying to make is that we are throwing large amounts of resources at our systems in order to keep iP levels down instead of just removing the waste organic material that ultimately leads to a significant amount of dissolved inorganic nutrients. we use GFO, algae, resins, carbon dosing to cover up the affects of the decomposition of the waste organic material. hoping to remove the iP from the water column at a rate that matches the dissolved iP of the environment we are trying to replicate. all of these are resources that would not need to be as necessary if the waste organic material was removed before it has a chance to decompose. yes iP is testable and gives us something to chase, but just looking to see the amount of biomass in the system can also tell you the amount of waste oP that is being produced and ultimately able to become dissolve iP.

As an analogy: the height of a dam and the size of the lake behind it doesn't necessarily have anything to with the downstream flow rate of the river. Running bare bottom to avoid accumulation of biomass and maintain a lower 'trophic' state is just lowering the height of the dam, but it's the flow rate of the river that we care about.

a BB dam would require less resources to hold back the water to maintain the desired water flow. the dam would not need to be made as strong, the valves holding back the water would not have to be as large. these are all resources (cost/maintenance).

I would argue that by the time you see it as detritus, most of the P that it's going to contribute to your system's rocks, water, and organisms has already been contributed. Unless you're siting in front of your tank with the siphon waiting for your fish to poop, or you vacuum every bit of uneaten food 2 minutes after you feed it, the detritus you're seeing is the end result result of the process, not the beginning. If you call using GFO to remove dissolved orthophosphate from the water top down, then vacuuming the undecomposable fraction of organic matter that collects in overflows and sumps as detritus is like top-top down. That phosphate is already in play.

as long as it is in solid form it can be removed. once removed it is not in play. if it is hiding in the substrate it is always in play. it takes time for decomposition to take place. it is not instantaneous. siphoning once a week will do wonders. you do not need to siphon every day. this is where the skimmer earns it keep. it is the only piece of equipment we use that actually exports P continuously. it makes sense to have the skimmer do as much as it can. have it see as much of the tank water as possible.

and that is why biodiversity and ecosystem are fancy words for phosphate sinks (cesspool)

Seems I keep diving in cesspools, aka one of one of the most biodiverse ecosytems on the planet...yup, you guessed it, the reef The ability of that diverse ecosystem to recycle nutrients such that the water on the reef is so nutrient poor, all the while the total nutrient levels of the reef on the whole are incredably high is something that is quite fascinating. Equally fascinating is our ability to recreate those cesspools (err, reefs) as well as we do.

I'm wondering, next class I take out to the sea grass beds, should I say "welcome to the cesspool, now jump in and start running transects"

it is important to know which type of reef someone is trying to emulate. the dissolved inorganic nutrient poor outer reef or the higher dissolved inorganic nutrient inner reefs. we need to setup our systems to match our must have organisms. why are we all told to setup our systems the same, when the organisms we keep can come from very different environments?

can we recreate the reefs even better if we would stop trying to setup all of our recreated reefs the same and start paying more attention to the environment that the organisms come from? if one wanted to grow sea grass, they would not use a BB system. if one wants to grow Acropora, then why have a substrate? i am just suggesting matching methodologies to the organisms wishing to be kept and understanding the pros and cons of each. that way the hobbyist can make informed decisions on what is more important to them and adjust for the pro's and con's to maintain the desired environment.

G~

 

[Randy Holmes-Farley]

you are correct. the point i am trying to make is that we are throwing large amounts of resources at our systems in order to keep iP levels down instead of just removing the waste organic material that ultimately leads to a significant amount of dissolved inorganic nutrients.

And if folks follow your advice and remove solid waste from the substrate, what is your quantitative evidence that they will no longer need to throw large amounts of resources at the systems in order to keep iP levels down?