The Faculative Zone

[subsea]

http://en.wikipedia.org/wiki/Facultative_anaerobic_organism

The efficiency of the bacteria in the "faculative zone" is the heart of the Jaubert Plenumn. The grain size of the media become the single most important componant of a successful sandbed.. Because of the larger grain size, the oxygan depletion gradiant is slowed down as the depth increases down thru the sandbed. This means that a larger volumn of sand has more faculative bacteria to do the job of denitrication.

http://www.chucksaddiction.com/cleanupcrew.html

Successful operation of a Jaubert sandbed plenumn requires many sand bed detrivores in my opinion. While it is not absolute to have these detrivore janitors, I use them so that I do not have to vacumn my sandbed. Also it is neat to look at these critters with a magnifying glass. My grandson and I explore this word of micro inverts with interest and enthusiasm. Sandbeds are large consumers of oxygen. Many disastors in captive reefs have occured due to low oxygen brought about by loss of electricity or circulating pumps. Once circulation stops, the sandbed consumes available oxygen at the expense of anything in the water column. Fish go first. I returned home after a week in the Smoky Mountains. Every fish in my 150G display tank was dead, aparantly after a day or two of the electrical interuption. After this disastor< I bought a whole house automatic start generator that would auto-transfer from the grid to my home unit.

I am also a big proponant of refugiums with mud systems. The more diversity in our nutriant pathways, the more success with reef keeping. This topic is the theme of how I do my reefkeeping. John Tullock put it nicely in the "The Natural Reef", Less technology, More Biology".

I look forward to discussion on this topic and it will be the theme of the April 16 Austin Reef Club Monthly Meeting at my home.

Patrick

[stoneroller]

Re: " the oxygan depletion gradiant is slowed down as the depth increases down thru the sandbed" I don't understand this statement and it's connection to grain size. Perhaps, an explanation of the Jaubert Plenum is in order.

[Derek]

The smaller the grains, the greater oxygen depletion as the sand bed depth increases. The large the grain the higher oxygen penetration depth.

[DaJMasta]

Specifically regarding denitrification though, isn't that an anaerobic process that only occours in the area of the sand bed without oxygen? I'm fairly certain that the break down of ammonia to NO2 and NO3 wll occour in the aerated portion of the sandbed (larger grain size is better), but if you want actual denitrification (the final step of that process to N2 gas) you need an anaerobic portion - the idea behind the deep sand bed - and thus a smaller grain size.

Also there's a lot of complexity regarding grain size. The larger the grains, the more space between them for oxygenation, but also the better chance they catch and retain detrius and the less overall surface area for bacteria to grow. While people have had success with virtually every kind of substrate, people seem to gravitate away from both extremes (Crushed coral and extremely fine sand), and there are now sands with a decent grain size difference which may work the best, especially after the smaller particles settle to the bottom.

[JasonJones]

I am not sure what we are supposed to be debating here, but I will throw a few thoughts out.

Deep sand beds are excellent at performing denitrification. But as suggested above, they also have the ability to deplete oxygen very rapidly in the event of a power loss. They also have a tendency to build up an excessive amount of nutrients over time if not properly maintained and became much more of a hindrance than a help as they can then release the nutrients back into the water. Many of these problems are alleviated through the use of a remote sand bed that can be taken off-line or replaced whenever problems arise, yet still provide the benefits of a deep sand bed. Also, to work properly, a sand bed must be deep (4-6"), which most people do not care to have in their display tank, yet another reason people use remote deep sand beds.

Also, the necessity of using deep sand beds for denitrification has decreased in recent years with the advent of new technology capable of performing the same function without the inherent problems. However, these new technologies may not provide all the benefits of a deep sand bed.

[subsea]

The smaller the grains, the greater oxygen depletion as the sand bed depth increases. The large the grain the higher oxygen penetration depth.

Derek, you are right on the money. Because the oxygen is depleted slower with larger grain size, then more volumn of sandbed is in the faculative zone and thus more de=ni9trification. Whoever said that anerobic bacteria are required for de-nitrification is wrong. While it is true that anerobic bacteria perform de-nitrification, they are extremely inefficiant, plus sulfate is a product of anerobic bacteria which produce de-nitrification. In other words, denitrification occurs in both the faculative zone as well as the anerobic section. The sulfate section of the bed can often be witnessed by a thin black line which migrates up and down.

I will not try to explain the Jaubert plenumn. There are plenty of scientific articles which do this in much detail.

Patrick

[stoneroller]

Well, if you had a smaller grain size you would have more surface area and could host more anaerobic bacteria than with say, a medium to large grain size. Even if anaerobes were less efficient at denitrification, then the simple fact that there are more "processors" (orders of magnitude more?) could lead to more effective conversion.

Come on, Patrick. What's the nickel definition of a Jaubert Plenum?

[subsea]

I have used Jaubert plenumns for more than 20 years and they have worked well for me. The larger grain size (1-4 mm) is important. I typically use "coral sand" packaged by Carribsea. It is arogonite and begains to dissove at about a pH of 8.0. The slower oxygen gradiant of the larger grain size increases both nitrification and the de-nitrification bacteria volumn. All of my sandbeds are at least 6'" deep.

The bottom 1" is the plenumn which is made with eggcrate at 1/2" thick and a 3/4" void. As I said at the beginning of this, "Less Technology / More Biology.

[stoneroller]

Sounds like my setup with no void. Why the void?

[subsea]

There is much debate on the necissity of the void. Many doctors of science have had conflicting opinions on the void. In the third series of Reef Aquariums, Charles Delbeek and Julian Sprung did an extensive evaluation of the Jaubert Plenumn. They compiled data over a 20 year period and concluded that the Jaubert Plenumn was far superior to other denitrification methods. I like it, it works for me. If you don't like it then don't use it. That does not deny the fact that it works very well.

[stoneroller]

I'm always looking to improve on my next setup.

Edited March 22, 2011 by stoneroller

[subsea]

Sounds like my setup with no void. Why the void?

I think that the void is necessaqry for the full benefit of this type of biological filtration. Delbeek and Sprung both feel that the void has merit. However, to throw away what you have gained by maturing this deep sand bed and starting over makes little sense. As with any husnbandry, techniques can be adjusted to the sysytem in question. I use mud filters in conjunction with Jaubert plenumns.

[Will]

Mud filters? Tell me more....

[stoneroller]

Do you recommend replenishing the plenum system by adding more sand on top? I've added some sand slowly on occasion but haven't replaced what has settled/dissolved fully.

[subsea]

Sand needs to be added over time. It dissolves at its own rate but it is easy to measure the loss in sand bed depth. Just add the proper substrate a little at a time. No more than 1" at a time.

With respect to mud filters, I usuallly grow macroalgae (seaweed). The sediment in a mud filter is the equivalent of oolite sand. The micro invert are much more numerous in this media. Refugiums feed the tank.

With respect to the sandbed becoming a niutriant sink, it is true to some extent. However, I look at it a different way. These are all nutriant pathways. Nutriants are obsorbed in the body mass of the micro inverts, bacteria and coral mass. Yes, the coral that you are growing is a nutriant sink and can give it back to the water column. I see no problem with sandbed critters and macroalgae absorbing nutriants from the water column. In fact, it is like an automatic compensating ecosystem. The more you feed it, the more it grows. When you stop feeding it, everything slows down and gradually self regulates. On numerous occassions, I have left the system unattended for months at a time.

[JasonJones]

I agree with you on your points completely with the caveat that the tank must be properly balanced- if that is the right term for it. People who let their tanks get very dirty well overwhelm a sandbed just as they will overwhelm other sources of filtration. However, with other sources, once overwhelmed they can be removed without any negative harm from the tank-replacement of a sandbed can cause problems.

But, properly maintained with the necessary critters and aquarium balance, I think a sandbed can be a create filtration system with the added benefit of great buffering capacity. My biggest concern has always been how permanent they are and how they can be overwhelmed by people whose husbandry skills could use a little work.

[DaJMasta]

Whoever said that anerobic bacteria are required for de-nitrification is wrong. While it is true that anerobic bacteria perform de-nitrification, they are extremely inefficiant, plus sulfate is a product of anerobic bacteria which produce de-nitrification.

That was me

But I think we're getting caught up in the naming system. The nitrogen cycle encompasses the whole thing, denitrification is the very last step in the cycle converting nitrogenous waste into nitrogen gas. The breakdown of ammonia, nitrates, and nitrites occurs in aerobic bacteria - yes - but then you've still got nitrates in your water. If you're really talking about denitrification - the removal of nitrogen from the system and thus the removal of nitrates without a skimmer/chemical means/growing macroalgae - and not just the breakdown of wastes, then you NEED anaerobic conditions like that of a DSB.

http://en.wikipedia.org/wiki/Nitrogen_cycle (works the same way on land as in the sea)

Thus my emphasis on the complexities of the sandbed. If you choose larger grain sizes you have the potential to catch more debris, but more 'filtration capacity' similar to that of what live rock gives you (the ammonia -> nitrite -> nitrate part). Smaller grain sizes means less oxygen in the sandbed, but unless you have the sand bed depth to make it completely anaerobic (oxygen is toxic to denitrifying bacteria), you will not get ANY denitrification from the system. That means going with a medium depth (2-4") sand bed is essentially useless in every situation except with really coarse sand (crushed coral), and then you run the risk of packing detrius into the gaps and needing gravel vacuuming and such. A shallow sandbed will be the most efficient otherwise unless you are looking for true denitrification, in which case as far as I know, DSB is the only option.

Now these are strictly nitrogen cycle concerns, there's certainly arguments to be made for the critters living in the sand as well as fish and things that need a certain kind of sand to survive.

[Timfish]

. . . My biggest concern has always been how permanent they are . . .

This is a concern of mine also. What filtering methodology or discipline lasts longer or is most likely to avoid "Old Tank Syndrome".

[subsea]

Faculative and anorobic are not the same thing. Twenty years ago when I was a waste water consultant I came across the "faculative zone". It was at the same time that I was operating my first Jaubert Plenumn. I have discussed this biology with many docotrs of science and am convinced of its efficiency. Like many things, if certain componants are not in place, it willl not work. Because of technique some people may not be able to operate a Jaubert Plenumn. Without a doubt, it is the most economical way to maintain a reef aquarium. I would venture to say it is the easiest method to maintain a reef. Remember, I have thirty years experience of trying this hobby out and I have done almost all of the methods.

If it works for you continue to do it. I will do the same.

[Will]

Can you please provide more information, as i am interested:

But from what i am understanding:

Faculative anerobes can survive in areas where there is o2 and can denitrate (all the way to N2) what is the rxn mechanism here if you dont mind me asking?

Obligative anerobes cannot survive in areas where ther is o2 and can denitrate (all the way to N2) but also convert S into H2S as thier final electron acceptor. Hence why you are saying that an obligative zone is "bad" and a Faculative zone is "good"

thanks

Will

[subsea]

Can you please provide more information, as i am interested:

But from what i am understanding:

Faculative anerobes can survive in areas where there is o2 and can denitrate (all the way to N2) what is the rxn mechanism here if you dont mind me asking?

Obligative anerobes cannot survive in areas where ther is o2 and can denitrate (all the way to N2) but also convert S into H2S as thier final electron acceptor. Hence why you are saying that an obligative zone is "bad" and a Faculative zone is "good"

thanks

Will

Will,

I am not familiar with the term rxn mechanism. The bacteria in the faculative zone denitrify with the release of nitrogen gas. The bateria in the anerobic zone produce much sulfate and some nitrogen gas. While sulfate in small quantities is good, too much is very bad. According to Julian Sprung, the use of the plenumn void has water with oxygen in it. This would allow O2 molecules to limit the anerobic zone from the bottom. In his third volumn of "The Reef Aquarium" Julian felt that the long term benefits of the Jaubert Plenumn took two or three years to become evident. He researced Jaubert Penumns set up for 20 years: no "old tank sydrome"

[Will]

reaction mechanism, how faculative denitirifing bacteria's reaction mechanism for converting nitrate to N2 compares to obligative anerobes and their mechanism for converting nitrate to N2, and why it releases H2S and other sulfur compounds.

IE how the reactions differ in the presence of O2 and in the absence of O2.

here is the RXN mechanism in a general sense

2 NO₃⁻ + 10 e⁻ + 12 H⁺ → N₂ + 6 H₂O

Do the 10 e's come from a sulphur compound?

Reduction under anoxic conditions can also occur through process called anaerobic ammonia oxidation (anammox):^[21]

NH₄⁺ + NO₂⁻ → N₂ + 2 H₂OIs this what occurs in the obligative zone?

some stuff i have found:

Aerobic denitrification or co-respiration the simultaneous use of both oxygen (O₂) and nitrate (NO₃^-) as oxidizing agents, performed by various genera of microorganisms.^[1] This process differs from anaerobic denitrification not only in its insensitivity to the presence of oxygen, but also in that it has a higher potential to create the harmful byproduct nitrous oxide.^[2] Nitrogen, acting as an oxidant, is therefore reduced in a succession of four reactions performed by the enzymes nitrate, nitrite, nitric-oxide, and nitrous oxide reductases.^[2] The pathway ultimately yields reduced molecular nitrogen (N₂), as well as, when the reaction does not reach completion, the intermediate species nitrous oxide (N₂O). A simple denitrification reaction proceeds as:

NO₃⁻ → NO₂⁻ → NO + N₂O → N₂ (g) The respiration reaction which utilizes oxygen as the oxidant is:

C₆H₁₂O₆ (aq) + 6O₂ (g) → 6CO₂ (g) + 6H₂O Classically, it was thought that denitrification would not occur in the presence of oxygen since there seems to be no energetic advantage to using nitrate as an oxidant when oxygen is available.^[2] Experiments have since proven that denitrifiers are often facultative anaerobes^[3] and that aerobic denitrification does indeed occur in a broad range of microbial organisms with varying levels of productivity, usually lower productivity than results from purely aerobic respiration. The advantages of being able to perform denitrification in the presence of oxygen are uncertain, though it is possible that the ability to adapt to changes in oxygen levels plays a role.^[1]

Im trying to understand the "science" behind the plenum in order to understand how it works. sorry if i got too technical

[Will]

found this too:

Sulfate reduction

The disimilatory reduction of sulfate seems to be a strictly anaerobic process as all the microbes capable of carrying it out only grow in environments devoid of oxygen. Sulfate (SO₄^-2 is reduced to sulfide (S^-2), typically in the form of hydrogen sulfide (H₂S). Eight electrons are add to sulfate to make sulfide

acetate + SO

₄

^-2

+ 3H

⁺

+

2CO

₂

+ H

₂

S + 2H

₂

O

Figure 4 - The reduction of sulfate to sulfide during growth on acetate.

The electron potential and energy yield for sulfate reduction is much lower than for nitrate or oxygen. However, there is still enough energy to allow the synthesis of ATP when the catabolic substrate used results in the formation of NADH or FADH. Substrates for sulfate reducers range from hydrogen gas to aromatic compounds such as benzoate. The most commonly utilized are acetate, lactate and other small organic acids (lactate, malate, pyruvate and ethanol are some examples). These compounds are prevalent in anaerobic environments where anaerobic catabolism of complex organic polymers such as cellulose and starch is taking place.

[subsea]

http://www.reefs.org/library/aquarium_net/996/996_6.html

You have not gotten too technical. Both articles are correct. If you need to get more technical, I must refer you to Sam Gamble's book on natural nitrate reduction. Also, I have some good information from Julian Sprung: Reef Aquariums Volumn 3. Follow the link above and you will get to the chemical equations. I learned this as an engineer. I understand the physics and chemistry but I can not give you the equations.

[subsea]

I remember a quote by Martin Moe (first person to raise clown fish). Martin has a pHd in marine biology and he made the comment to many other doctors of science at one of the first MACNA Conferences in reference of captive reef keeping. "It is not rocket science, it is more complicated". Some of the things that we are doing in the reef hobby is way ahead of the education community. It is exciting times in this hobby for me. There is so much new stuff going on all the time. I remember using an undergravel filter with crushed up oyster shells from the chicken feed house. I bought the oyster shell media for $.10 per pound. I set up a Galveston Bay habitat and collected critters from the marsh estuary. As I recall this tank, I am still struck with the beauty of this underwater world. No colors but contrast in black and white which suggested the beauty to be found in this underwater world. While I have never scuba dove on a reef, I have snorkled on a reef. For me as I quietly floated by a coral head, remaining motionless, a world came alive in front of my mask. I am hopelessly hooked on the hobby. As I listen to comments, I know there is an intelligent community eager to digest information and use knowledge to interput results and findings. Sometimes these deductions may not be right, but the inquisitive mind continues to seek the truth, as do I. I am happy to share insights and deductions and enjoy debating these deductions. There is only one truth, but there are so many layers we often get lost chasing a rabbit trail.

Patrick