DSB Plentum or Not?

[the plumber]

Hello All,
I just purchased my deepsouth sand and am going to remove rock and critters this week to start my DSB.
My question to you is.... Should I build a Plentum for under the 4-6" of sand or not?
My research says no but I have heard thru other hobbiest that I should!
Before I do all the removal I thought I would ask the good knowledged folks at TRT forum.
Thanks in advance to your post,
Dave

[SteveNichols]

It is more difficult to set up, doesn't have any advantages over a DSB, at least that i have ever heard. Use the sand alone.

[Hommeworks]

Get the pamphlet ' Live Sand Secrets'(Amazon) by Dr. Bob Goemans. What you are thinking about is referred to as the Monaco System developed by Dr. Jaubert. In theory you should need just a plenum, DSB and no skimmer. It is suggested that regular water changes be schedlued. This system promotes an efficient chemical sink that doubles the nitrogen cycle.

I installed a plenum, but I do agressive protien skimming along with bi-weekly water changes of my sump volume. My nitrite levels are barely distinguishable. Nitrates are under 3ppm.

I can't swear if the plenum makes a difference. This is my 1st aquarium. I just jumped out there and added a plenum.

Just a couple of fish, lots of SPSs, torches, hammers, and a big pavona. 155gal with 120lb of LR.

[horge]

Just thought you might enjoy a little entertainment:
To be fair, we were all irritable that very cold morning, and I do not know for a fact that the statements that are refuted below actually came from R. Goemans' pamphlet or not.

These are from a rather spirited online exchange earlier this year.

Anyway, enjoy:


*********

Anthony asks:
I have a 150gal reef/fish tank set up now for 3 years. I made the mistake of going with a UG filter setup with 3" of aragonite sand on top of the UG filter.

My problem has been nitrates. I can't keep my nitrates under 100ppm. I can change 20% of the water and test my tank the next day and it is still 100+ppm nitrates...

So, I have been reading up on DSB's...
I was convinced that the DSB method seems to be the best until I read up on plenum systems.

In particular a book called "Live Sand Secrets", Revised 2nd Edition. It is written by Bob Goemans, Ph.D.

In this book it goes on to explain why a DSB is not as good
as a plenum. I was hoping you could tell me if what Bob Goemans explains is correct in what he is saying. Below are a few key points he brings up.

1. "There is also some thought that very fine sand grains, 1mm or less make for a good sand bed whether its a deep or shallow sand bed directly on the aquarium bottom. The thought here was that if there were more sand grains, there would be more bacteria. That is true. Unfortunately they are the wrong type bacteria! There is very little penetration of oxygen through fine grain sediments because the sand grains are very close to each other. This results in little space, called pore water, around each sand grain for dissolved nutrients to penetrate. In fact, oxygen penetration may only be a millimeter or two in depth and the anoxic layer may be the thickness of a piece of paper. Not truly conducive to a long-term balanced environment."

2. "The plenum itself is a reservoir for a very small amount of oxygen and some nitrate. Its oxygen insures that the four-inch layer of sand above the plenum will remain anoxic (about .5 to 2 mg/l), not anaerobic. Nitrate reserves in the plenum provide an energy source for the abundance of very efficient reducing bacteria in the above sand bed. In the sand bed above the plenum, some of the microbial processes reduce nitrate to a harmless gas. "

3. "In my original articles I referred to the plenum area as a stagnant area. But that was far from true as we now know there's a great amount of diffusion occurring in the plenum. Its chemical parameters are constantly changing and having sufficient open area under the grid facilitates their chemical movements."

4. "DSB or sand/rock only setups result in Ammonification which is mostly Anaerobic Heterotrophs. Very limited energy transformation due to limited oxygen content in sand/rock only.

Plenum/Sand Bed setups result in Anoxic Denitrification which mostly Aerobic Heterotrophs. Dissolved oxygen in plenum and lower sand bed promotes higher energy transformations, increasing denitrification yields and size of bacteria colony."

5. "Because of his (Sam Gamble, Aquarium Biologist at the John Pennekamp Coral Reef State Park in Key Largo, Florida)perseverance on this subject matter aquarists now have a better understanding of live sand microbial processes. We now know the plenum system, with its greater volume of properly conditioned live sand, is "biologically" more efficient than sand beds directly on the bottom of the aquarium or that of live rock. In fact the plenum-equipped live sand system has proved to be an improvement on what is found in nature!"

6. "The important point here is that very efficient biological processes are occurring in the upper inch of live sand. Below that, in the ocean and sand beds directly on the aquarium bottom, a less efficient form of biological filtration is occurring. Because there is such a tremendous sediment surface and volume of water in the oceans, those deficiencies found in their lower sediments are easily overcome. The same is not true in a closed system. Moreover, the less efficient form of biological filtration can easily become prevalent because there is simply less water volume when compared to that in nature. That is unless the more efficient portion of the closed system's sand bed area is extended downward with the installation of a plenum!"

Sorry for the long post but I think many good points are made here. I am now leaning toward going with the plenum design but want to get your thoughts on this before I go through with it.
Thanks for your time and help in advance!!!

Anthony


****************************
Ronald from Montana replies:

quote:
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1. "There is also some thought that very fine sand grains, 1mm or less make for a good sand bed whether its a deep or shallow sand bed directly on the aquarium bottom. The thought here was that if there were more sand grains, there would be more bacteria. That is true. Unfortunately they are the wrong type bacteria! There is very little penetration of oxygen through fine grain sediments because the sand grains are very close to each other. This results in little space, called pore water, around each sand grain for dissolved nutrients to penetrate. In fact, oxygen penetration may only be a millimeter or two in depth and the anoxic layer may be the thickness of a piece of paper. Not truly conducive to a long-term balanced environment."
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Wrong. See my articles on sand beds and water movement.

quote:
----------------------------------------------------
2. "The plenum itself is a reservoir for a very small amount of oxygen and some nitrate. Its oxygen insures that the four-inch layer of sand above the plenum will remain anoxic (about .5 to 2 mg/l), not anaerobic. Nitrate reserves in the plenum provide an energy source for the abundance of very efficient reducing bacteria in the above sand bed. In the sand bed above the plenum, some of the microbial processes reduce nitrate to a harmless gas. "
----------------------------------------------------

Nitrate is reduced to nitrogen gas, which is biologically inert. As it makes up the majority of the atmosphere, we had better hope it is not toxic.

quote:
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3. "In my original articles I referred to the plenum area as a stagnant area. But that was far from true as we now know there's a great amount of diffusion occurring in the plenum. Its chemical parameters are constantly changing and having sufficient open area under the grid facilitates their chemical movements."
-------------------------------------------------------------------

Diffusion has almost nothing to do with what is occurring in a plenum or sand bed. In any case, both systems are relatively dynamic.

quote:
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4. "DSB or sand/rock only setups result in Ammonification which is mostly Anaerobic Heterotrophs. Very limited energy transformation due to limited oxygen content in sand/rock only.
--------------------------------------------------------------------

Ammonification definitely does occur, and this material is then converted to nitrates and subsequently to nitrogen gas which leaves the system harmlessly.

quote:
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Plenum/Sand Bed setups result in Anoxic Denitrification which mostly Aerobic Heterotrophs. Dissolved oxygen in plenum and lower sand bed promotes higher energy transformations, increasing denitrification yields and size of bacteria colony."
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The above occurs in sand beds, but not in plenums to any great degree, and it is the reason that plenums are less efficient at removal of nutrients.

quote:
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5. ..... aquarists now have a better understanding of live sand microbial processes. We now know the plenum system, with its greater volume of properly conditioned live sand, is "biologically" more efficient than sand beds directly on the bottom of the aquarium or that of live rock. In fact the plenum-equipped live sand system has proved to be an improvement on what is found in nature!"
------------------------------------------------------------------

Absolutely false.

quote
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6. "The important point here is that very efficient biological processes are occurring in the upper inch of live sand.
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This is true.

quote:
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Below that, in the ocean and sand beds directly on the aquarium bottom, a less efficient form of biological filtration is occurring. Because there is such a tremendous sediment surface and volume of water in the oceans, those deficiencies found in their lower sediments are easily overcome.
----------------------------------------------------------------

The anaerobic processes are normal and not deficiencies, but rather the "next" steps in the reduction and elimination of excess nutrients.

quote:
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The same is not true in a closed system.
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This statement is false. . I would also point out that a plenum system is just as "closed" as is a sand bed.

quote:
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Moreover, the less efficient form of biological filtration can easily become prevalent because there is simply less water volume when compared to that in nature.
--------------------------------------------------------------

Water volume has nothing to do with anything. Indeed you will have these zones of filtration - you want them - as they complete the processing nutrients in lower sediment areas.

quote:
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That is unless the more efficient portion of the closed system's sand bed area is extended downward with the installation of a plenum!"
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A well constructed sand bed has a deeper layer of this zone than does a plenum because the animal life in it creates the zone well within the sediments.

quote:
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Sorry for the long post but I think many good points are made here.
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No, as point of fact, No good points were made here. This author has no scientific background and he is unaware of the basic processes occuring in the sediments.


*******************************
Porgy from the Philippines replies:

Let's see...

quote:
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Originally stated by B. Goemans (?)
1. "There is also some thought that very fine sand grains, 1mm or less make for a good sand bed whether its a deep or shallow sand bed directly on the aquarium bottom. The thought here was that if there were more sand grains, there would be more bacteria. That is true. Unfortunately they are the wrong type bacteria! There is very little penetration of oxygen through fine grain sediments because the sand grains are very close to each other. This results in little space, called pore water, around each sand grain for dissolved nutrients to penetrate. In fact, oxygen penetration may only be a millimeter or two in depth and the anoxic layer may be the thickness of a piece of paper. Not truly conducive to a long-term balanced environment."
-----------------------------------------------------------

Depending on the environment this can possibly be true (like if you poured epoxy atop a DSB? J/K!). Obviously, if a DSB is to be made a purely bacterial proposition, then Mr. Goemans'(?) thinking can apply: no bugs, worms and molluscs moving around the bed. But since when have we seen a purely bacterial DSB being proposed?

First Mr. Goemans(?) makes the claim that nutrient transport is restricted by a sandbed's limited 'pore space' --a term better applied to monolithic, as opposed to aggregate media. Let's call it void space.

Even IF you assert that fluid movement is nonexistent within a DSB, and that it's just diffusion you're relying on (and I would vigorously contest so simplistic an attestation) --why then claim that the anoxic layer would be paper-thin?

Look, if you've got restricted transport through the bed, then O2 also stays up on deck: you will have an anoxic or hypoxic layer as THICK as the sandbed, not paperthin! (such obviously is neither what DSB enthusiasts observe, nor what they seek, but the lapse in logic was glaring)

You cannot argue (elsewhere) that a DSB becomes a nutrient sink while denying the very transport mechanism you base the sink process on: if waste can get down there, so can oxygen, and it's all a matter of managing the gradient of penetration for each via sandbed component selection.


quote:
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2. "The plenum itself is a reservoir for a very small amount of oxygen and some nitrate. Its oxygen insures that the four-inch layer of sand above the plenum will remain anoxic (about .5 to 2 mg/l), not anaerobic. Nitrate reserves in the plenum provide an energy source for the abundance of very efficient reducing bacteria in the above sand bed. In the sand bed above the plenum, some of the microbial processes reduce nitrate to a harmless gas. "
--------------------------------------------------------------------------------


I think the terms Goemans(?) sought were anoxic and hypoxic, as in "the four inch layer of sand above the plenum will remain hypoxic (insert measurments here), not anoxic". The first term can be appended to low-oxygen environments, and the second to oxygen-free environments. Anaerobic is a term really reserved for biological processes, NOT the environment such a process can take place in.

Otherwise, Goemans'(?) above is just a restatement of common knowledge regarding aerobic and anaerobic bacterial reduction of niotrogemous waste. If you can grant that accumulated nitrate in the plenum can feed the bed above, then all it takes is acceptance of trans-DSB movement of nitrogenous waste to award DSB the same virtue.



quote:
--------------------------------------------------------------------------------
3. "In my original articles I referred to the plenum area as a stagnant area. But that was far from true as we now know there's a great amount of diffusion occurring in the plenum. Its chemical parameters are constantly changing and having sufficient open area under the grid facilitates their chemical movements."
--------------------------------------------------------------------------------



If you tight-focus on just diffusion as the mechanism for transport, you shoot yourself in the knees. Fluid-motion transport throught the sandbed HAS to be present: at the very least, escaping bubbles of gaseous N have to be replaced by an equivalent volume of water or you have a vacuum, and where does that water come from? An alternate dimension? No, it comes from the sandbed above, and THAT water hads to be replaced by water from further upstairs, effecting minimum fluid transport. And that's the minimum.

I suggest that if you will swish the water topside, you're going to get some feedback motion in the fluid between grains no matter how small or deep --so long as there is a fluid connection between them: DSBs or plenum-SB's. DSB's though, seem better suited to hosting a natural profile of sandbed inhabitants.



quote:
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4. "DSB or sand/rock only setups result in Ammonification which is mostly Anaerobic Heterotrophs. Very limited energy transformation due to limited oxygen content in sand/rock only.

Plenum/Sand Bed setups result in Anoxic Denitrification which mostly Aerobic Heterotrophs. Dissolved oxygen in plenum and lower sand bed promotes higher energy transformations, increasing denitrification yields and size of bacteria colony."
--------------------------------------------------------------------------------


Could Mr. Goemans (or whoever wrote the above) repeat all that in English, please?

Seriously, there is again an assertion that Plenum-SB's have a corner on oxygen distribution. You cannot argue that the plenum is anoxic, and THEN claim the Plenum-SB is better oxygenated because it's exposed top AND bottom.

And anyway, if you thusly want to stick to aerobic bacterial reduction as your ace, then you're kneecapping your system by limiting the quantity of anaerobes that will effect final reduction of processed crud into gaseous N.


quote:
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5. "Because of his (Sam Gamble, Aquarium Biologist at the John Pennekamp Coral Reef State Park in Key Largo, Florida)perseverance on this subject matter aquarists now have a better understanding of live sand microbial processes. We now know the plenum system, with its greater volume of properly conditioned live sand, is "biologically" more efficient than sand beds directly on the bottom of the aquarium or that of live rock. In fact the plenum-equipped live sand system has proved to be an improvement on what is found in nature!"


6. "The important point here is that very efficient biological processes are occurring in the upper inch of live sand. Below that, in the ocean and sand beds directly on the aquarium bottom, a less efficient form of biological filtration is occurring. Because there is such a tremendous sediment surface and volume of water in the oceans, those deficiencies found in their lower sediments are easily overcome. The same is not true in a closed system. Moreover, the less efficient form of biological filtration can easily become prevalent because there is simply less water volume when compared to that in nature. That is unless the more efficient portion of the closed system's sand bed area is extended downward with the installation of a plenum!"
--------------------------------------------------------------------------------


Again, there is the presumption that reef sediments and DSB's, are hardpack, concretious affairs that block out fluid movement and transport of both nitrogenous waste AND oxygen. Too many factors, from the wee beasties wriggling around the grains, to the nature of water movement in the system ought to be reckoned before making such a presumption.

While we're at it...
I guess if bacterial modes of dispatching unwanted nutrients are your only option, then you have a case for touting the virtue of having truckloads of bacterial media. But it ISN'T just bacteria, is it?

Just to be clear, I have nothing against Plenum DSB's in all their conceptual simplicity (that is, based on the above-quoted statements, I take them to be simplistic) ...and I actually have a great number of nits to pick with DSB's (and Ron is probably weary of my whining, hehe), though a DSB's very dynamism MEANS there will at least be the nit of voodoo variability to pick.

I just have a great deal of discomfort with apparently distorted reasoning used as attack or praise towards either.

*************

Just points to consider before going for a plenum...

[Spanky]

Dave here's a link to a paper in the archives that Chris wrote on Jaubert.

http://www.thereeftank.com/forums/sh...=&threadid=745

Now if you'll excuse me, I have to take a ride up to Key Largo and slap Sam - again!

[Ninong]

Dave,

Just in case you didn't pick up on it in the articles that have been referenced, your Southdown sand is not the appropriate particle size for constructing a plenum system. That is a very important consideration. It is, however, excellent for use in a good old fashioned DSB without a plenum.

Should you choose to construct a plenum, be sure to use the appropriate size coral sand and gravel for the lower anaerobic layer and the appropriate size for the upper aerobic layer. Those layers should be divided by a screen. Starting at the bottom of the tank you have the confined water space, then a plate/screen, then the anaerobic sand and gravel, then another screen, then the upper aerobic sand layer. The exact size of these layers depends on the total volume of your aquarium.

It is very important that you set up the plenum correctly because, according to Dr. Jaubert, the confined water should have an average oxygen concentration of 1 mg/l. If it rises above 1.5 mg/l, denitrification will be incomplete and you will get excess nitrite and if it falls below 0.5 mg/l you get hydrogen sulfide. So be careful.

In the paper written by Chris that Spanky linked, there is mention that some sources have incorrectly stated that Dr. Jaubert's system is "open" to the Mediterranean. Chris correctly points out that Dr. Jaubert's original experimental system was operated for 4 years with no water changes. I wonder if there is some confusion here with the Jaubert system that is employed at the Monaco Aquarium? As I have pointed out in several posts, the tanks at L'Aquarium du Musée océanographique de Monaco are open to the Mediterranean. These tanks are operated on Jaubert's Microcean Process (patented by Jaubert) but they use fresh filtered/sterilized water from the Mediterranean. (Not unlike the Waikiki Aquarium which uses fresh water from the Pacific.)

Here is a picture of the Monaco Aquarium:



Here is a drawing of the setup of the Monaco Aquarium:


L'eau de mer est aspirée par une pompe (1) à travers une crépine (2) située à 55 mètres de profondeur afin d'obtenir une eau propre et fraiche. Elle est ensuite refoulée dans une cuve de décantation (3), puis remonte jusqu'à une tour de pression (4) d'où elle descend par gravité, après passage dans d'autres cuves de décantation, vers l'Aquarium et les laboratoires (5).


La filtration
L'eau est ensuite filtrée puis stérilisée, avant d'être distribuée dans les bassins. Certains fonctionnent en circuit ouvert avec un renouvellement d'eau permanent, d'autres sont en circuit semi-fermé ou encore en circuit totalement clos, comme cela est le cas pour les bacs tropicaux.
L'ensemble du dispositif permet de faire circuler jusqu'à 400 000 litres d'eau par jour. Tous les points-clés du système (pompes, filtres, canalisations...) sont doublés pour pallier toute défaillance éventuelle


According to Delbeek (1994) "No water changes are performed for some systems, though some at the Aquarium in Monaco receive 5% per month water changes."

According to the Monaco Aquarium's own website, they circulate 400,000 liters of fresh filtered and sterilized water from the Mediterranean on a daily basis. I could be wrong, but that sounds like more than 5% per month. Some of their tanks are on a constantly open circuit and others are on a partially open circuit. They describe their system here: http://membres.lycos.fr/aquafrce/Monaco3.html

The Monaco Aquarium is the most famous advocate of Jaubert's plenum system and it is often cited in articles discussing that system. It is important to note that since the Monaco Aquarium is open to the sea, it is not representative of what one could expect as far as calcium stability is concerned in their own closed system reeftank.

[galleon]

"Now if you'll excuse me, I have to take a ride up to Key Largo and slap Sam - again!"





Seriously, Sam's new lackey, Bob, originally *******ized (can I use that word here?) the entire (and completely legitimate) concept that Prof. Jaubert developed for captive coral research. Read an article by Dr. Erich Mueller, Dr. Jaubert himself, or the one Jerel posted. Not Bob's booklet.

Thanks Ninong. Just another general FYI, several institutions are currently using closed Microceans to great success. Particularly notable is the Center for Tropical Research in Summerland Key. This is the lab that Dr. Mueller heads up.

[Ninong]

Galleon,

As an aside, do you happen to know in which field Bob Goemans has his Ph.D.? Ron always alludes to the fact that it is irrelevant to our hobby without actually saying exactly what he means.

[foobuddha]

Ninong,

I did a google search and Bob Goeman's bio from the IMAC registration site says he has a doctorate in business management.

[Piero]

.

[Spanky]

Particularly notable is the Center for Tropical Research in Summerland Key. This is the lab that Dr. Mueller heads up.

Yep, right next door to Bob's place. Might as well head to Home Depot in Marathon tonight and slap two more on the way!

In all honesty, personally I think DSB's, plenums, etc are all too much trouble.

[the plumber]

Thanks to all that have replied!

After reading Dr, Bob's articles and your generous input, I have decided to just use a DSB.

Thanks again,
Dave

[ShirleyM]

Over four years ago when we set up our first reef tank, we all did a ton of research, including reading Goeman's booklet. It seemed the way to go was with a plenum, and a local reefer had one in his 220G tank, and it seemed to work for him, altho in hindsight I recall a lot of hair algae in that tank...it had been up for about 6 years. I dind't know much about hair algae back then.

4 months later when we set up the 120G reef, we again researched and considered and thought about it, and ended up putting in a plenum. Same with the 125G FOWLR.

For the past year I've been wondering if we should have just had a proper DSB. However, the results with the plenum systems have not been consistent:

Troy's 30G reef w/plenum: 0 nitrates almost all the time. Hair algae and bubble algae problems - yes.

120G reef w/plenum: Still can't get the nitrates below 25 ppm. No, our water changes aren't often enough. pH is much better (higher), though (8.0-8.1) Phosphates 1.0 Still have hair algae problems on a few rocks and back wall. (no hair algae whatsoever first 2-1/2 yrs)

125 FOWLR w/plenum: Since last May we've been feeding MUCH less "soup" and nitrates have dropped from 100+ to maybe 75 ppm. No algae problems.

10G minireef, DSB no plenum: No algae problems, maybe 5 or 10 nitrates.

We USED to be able to keep LPS and SPS corals in the 120G. Now it's hit and miss, so we don't try (Frogspawn has lived throughout, as has meat coral)

After reading Chris's article last May I figured we did the plenum all wrong b/c the sandbed is not blacked out on the sides, and it probably isn't deep enough, and maybe the sand is the wrong size.....(very frustrating not knowing exactly what to do)

So, this is partly commentary and just sharing with no intent of passing on worthwhile knowledge or experience, and ...

part in asking the question....IF we ever decided to tear down and redo the 120G.....would that even be remotely possible?? Wouldn't the water under the plenum contaminate all the rest of the water?? wouldn't we have to wash all the live sand?? Is starting over ever an option when you have healthy fish and corals that have been healthy for 3-4 yrs?? (We just have trouble getting NEW corals to like it there, and I can't get rid of the algae on a couple of the larger rocks and back wall).

I should add that during this time period Troy was doing a research paper on Aquaculture and Propagation of Corals and was in contact with a research grad student in MD, and he [grad student] was researching plenums and had all the diagrams up on his Website, which I no longer can find, and his design was the one that inspired us, so it wasn't just Goemans that pushed us in that direction. Everything this fellow said made scientific sense to use a plenum. He had a lat of data collected that made sense at the time...

TIA,
Shirley

[Dipstick]

What is a plenum ?

[ShirleyM]

Hi Drew,

I tried to find you a link with a pic, but can't at the moment.

I'll paste a definition here from another board....the link to it wouldn't work.

A plenium is a 1 to 1-1/2" water void under the sand bed. It is created by placing eggcrate and a screen over it to keep sand from filling the space. It covers the tank bottom less an inch or so around the edges. The sand is 4 inches deep..... The people for it say it is supposed to be a more efficient form of nitrate reduction as compared to a DSB. This is where the debate starts and where I will leave it.

hth,
Shirley