Discussion of the Week ~DSB and Plenums~

[mojoreef]

Alright folks as personally requested by Galleon this weeks topic id DSB's and Plenums. This has the chance to be a great topic and a strong debate. So lets hear it. How do u set up a DSB, what shows you its working, are plenums worth the hassle or do they perfom the same job. Whats important in setting up a DSB or Plenum.

Lets hear it folks

Mike

[galleon]

ROCK ON! Thank you Mr. Mojo Risin'.

Before anybody goes plenum bashing, please peruse: http://www.thereeftank.com/article/jaubert.htm

Thank you for your time
Chris.

[mojoreef]

Aah I was setup,lol. Great article chris, I have a bunch of questions for you on some stuff in though I need to take some meds and I will get back with you on them

thanks

mike

[galleon]

Meds...lovely I eagerly await your questions.

[Reedman]

Galleon,

first, great article. It clears a lot of the misconceptions about plenums. I have nothing against plenums, but I don't understand what it is about the void space that a plenum system requires that is any different from what the lowest levels of a DSB provides. It seems that the DSB method should do the same thing without needing to worry about a hole developing in the screen of the plenum.

Again, not bashing, just curious.

-Reed

[mojoreef]

Ok I am medicated, lol So I will start by saying anything I may saw now is done so under the influence of drugs and I hold myself harmless.

In your article thier were a couple things I would like to hear more on.
1 On the particle side of the plenum you mentioned the use of sediment of 2mm. To me this sounds rather large. Wouldnt it be better to go with a smaller sediment in order to have more surface area for the grow of bacteria. Also froim my experence with larger sediments, fauna tends not to stay in it as much as with the smaller sizes, this reduced the amount of travel through the sandbed which inturn kinda screwed up the whole process.

2 Now maybe I misunderstood, but it seemd like the way you were discribing the system was that it would take care of all the elemental replenishing and that the use of kalk and reactors actually createan ionic imbalance. Now I agree that kalk and reqactors do feed the elements heavy and usually not perfect, but I think it would be alot to ask of a plenum system to replenish the elements of a tank that houses so many calcium and carbonate requiring inhabitants.

your tought while I go blow my nose

Mike

[galleon]

Mike,
re: particle size.
In general, grain sizes smaller than 1.5-2 mm in a microcean tend to reduce the large amounts of diffusion necessary to process nutrients and dissolve the carbonate sand. This is why it is important to have a sandbed with an adequate enough overall area, which shouldn't really be a concern with the length of most aquaria. Smaller aquaria can use remote "reactors" (as Jaubert calls the sandbed/plenum space) in wide/short tanks to help increase overall area (in Monaco, the tall, thin tanks use these). There is still plenty of fauna that can dwell in sand this size (CaribSea Geo-Marine), polychaetes, etc. Their function is slow turbulence of the sandbed, so they have to be large enough to move the larger sand grains anyway.

re: elemental replenishment.
That's just the way it works. The carbonate sand dissolves enough to support a full compliment of rapidly calcifying coral genera such as Acropora and Pocillopora. Dr. Jaubert in Nice and Dr. Erich Mueller of the Center for Tropical Research exclusively used closed system Microceans for duplicating reef conditions to the point where they are used for "accurate" coral reef research/expermental design. Erich is using the Microcean to grow "crops" of explants for reef restoration experiments. His tanks are full of Acropora cervicornis and Montastrea sp., etc. I can tell you from empirical experience that Acropora cervicornis grows like nothing you've ever seen in your life, too. It is a true weed of the coral world.

Reedman, the plenum space is the pool for the lower pH water in the "reactor"

[mojoreef]

OK again on the particle size, the smaller the particle the the overall surface area you have for bacteria to live and do thier job. Also with a larger particle size it would seem that you would not see the anaerobic until you went a lot deeper and the larger particles will allow for more transmission of oxygenated water. Or are you say the the reactor zone is where they hang out.

Ok on to the dsb theory. what would you say is the difference bewteen the overall function of a deepsand bed and that of a plenum. as in do u have any pros and cons


mike

[galleon]

"Also with a larger particle size it would seem that you would not see the anaerobic until you went a lot deeper and the larger particles will allow for more transmission of oxygenated water. Or are you say the the reactor zone is where they hang out."

Mike, trust me, 4-6 inches of 2 mm sand is plenty deep for O2 levels to get to 1.5 mg/L and below in the lower areas of the sandbed.

I'd say the main difference(s) in DSB and Microcean are that the Microcean provides a complete captive ecosystem by the release of dissolved aragonite components. Also, the fauna species representation in the Microcean is more accurate compared to a real reef than the DSB, because the sand particle size is more congruous.

[mojoreef]

I'd say the main difference(s) in DSB and Microcean are that the Microcean provides a complete captive ecosystem by the release of dissolved aragonite components. Also, the fauna species representation in the Microcean is more accurate compared to a real reef than the DSB, because the sand particle size is more congruous.

I would tend to lean your way on the fact that the Microcean system maybe more simular to that of a reef area, but I really dont think that it is as productive as a true DSB 9I dont have any data that I can look at that would show me the differences in the ammounts of dissolved argonite, so I will give you that maybe the plenum might be more productive in that case (but really only a guess on my part)

As per the effectiveness of the plenum over a DBS for nutrient removal and/or conversion I would like to dig a little deeper
I believe that a DSB out performs a plenum in this case. My reasoning as follows.
1 the particle size of a properly set up DSB is much smaller thanthat of the system u discribed. This will increase the overall surface area in which will be populated with bacteria and other fuana. Thus allowing for more processing (critters) for the task at hand.
2. this partiucle size will also allow for a more densely and more diverse populations of fuana. I beleive thier have been many studies that shown the populations of finer beds out do the coarse sometimes by the hundredes of thousands per sq meter. I beleive this will also make the DSB more efficient.
3. with a larger particle size sediment and the high water flows most of us have in our aquaria, i beleive oxygenated water will be more prevalent deeper in the bed. this would also go with light penetration. this would mean that the anaerobic zone would be farther down (hard for the passage of nutrients and possible smaller zones)

these would be a few questions for ya Galleon in regards to the one versus the other. Also on the plenum system reactor zone (the area under the plenum) i would imagine with the lack of sediment for the population of fuana that this zone is basically just for the disolving of the sediment above? and what would you think about the possibility of nutrient storage in this zone? if its thier, there is always the posibility of it being release back into the tank.

thanks buddy, looking foreward to your reply.


mike

[galleon]

but I really dont think that it is as productive

Neither of them are productive. Productivity refers to organic carbon produced by photosynthesis or chemosynthesis. You want denitrifying zones to be the opposite of productive

2. this partiucle size will also allow for a more densely and more diverse populations of fuana. I beleive thier have been many studies that shown the populations of finer beds out do the coarse sometimes by the hundredes of thousands per sq meter. I beleive this will also make the DSB more efficient.

Our goal is a reef tank, yes? We want species diversity that mimics a reef as close as possible without sacrificing system functionality, yes? Well, a DSB doesn't come close. These large populations of organisms that live in fine sand to silt size particles do not live on the reef zone we're trying to create. The Microcean creates more accurate population/species diversity without sacraficing the functionality of the system. DSB's cannot do this.

3. with a larger particle size sediment and the high water flows most of us have in our aquaria, i beleive oxygenated water will be more prevalent deeper in the bed. this would also go with light penetration. this would mean that the anaerobic zone would be farther down (hard for the passage of nutrients and possible smaller zones)

Actually, we don't have high water flows. Not compared to real reefs. Using coarser, heavier particles allows you to implement more water flow in the tank without disturbing the sandbed physically. According to Jaubert, high circulation in the bulk water does not effect the oxygen levels in the lower levels. With a fine DSB, high/more accurate water energies will disturb the sandbed physically, and this will destroy denitrifying potential.

this zone is basically just for the disolving of the sediment above?

This zone is where the acids produced by the bacteria can diffuse to and lower the pH of a large enough volume of water (the plenum space) to dissolve the carbonate sand.

what would you think about the possibility of nutrient storage in this zone?

To my knowledge, no one has comprehensively examined this. Theoretically, the diffusion of the inorganic nutrients through the sandbed, the bacteria should complete their processes on the nutrients before they pool underneath the sandbed.


Just as an endnote, I do not believe sandbeds are necessary in the slightest when it comes to a successful reef system. I've been culturing Atlantic corals for 4 years now in a continuously running Berlin system. No sand, Highly lit, Highly skimmed, particulates filtered, heavily fed, 3 separate surge devices in 100 gallons of water, UV sterilized, with lots of live rock. Our growth rates are phenomenal. Regular, weekly water changes and addition of only CaCl2, HCO3, and CO3. Never a hiccup with the system.

[mojoreef]

Neither of them are productive. Productivity refers to organic carbon produced by photosynthesis or chemosynthesis. You want denitrifying zones to be the opposite of productive

Ok maybe I worded that wrong would you not think with what I stated about the fuana and surface area for the fuana to populate that the DSB would be better at denitrifing.

Our goal is a reef tank, yes? We want species diversity that mimics a reef as close as possible without sacrificing system functionality, yes? Well, a DSB doesn't come close. These large populations of organisms that live in fine sand to silt size particles do not live on the reef zone we're trying to create. The Microcean creates more accurate population/species diversity without sacraficing the functionality of the system. DSB's cannot do this.

Ok I can only speak for myself but my goal is to sucessfully keep corals in a natural system. and I do understand that a DSB mimics a lagoonal area rather than a reef zone. Iand I do beleive that the microcean does more accurately reflect the sediment in a actual reef, BUT the reason I would use a DSB or a PLenum would be for its nutrient processing ability, not for which is closer in looks or actuality to the reef zone. So in that thought it would go back to the original question. Knowing that a lagoonal concepted DSB contains hundreds of thousands more nitrifing fuana than that of a reef sedimant based system would it not be better in the case of denitrifing?

Actually, we don't have high water flows. Not compared to real reefs. Using coarser, heavier particles allows you to implement more water flow in the tank without disturbing the sandbed physically. According to Jaubert, high circulation in the bulk water does not effect the oxygen levels in the lower levels. With a fine DSB, high/more accurate water energies will disturb the sandbed physically, and this will destroy denitrifying potential.

agreed

For me the use of either a DSB or a plenum will come down to which will offer the best source of dinitrification. The additional benefit of replenishing the elements is a definate plus. Do you not think that the same disolving of argonite would occur in the lower reaches of a DSB


Mike

[aquaticsdeptleader]

not that i know much but it would seem logical that lagonal type areas would trape more waste products then your typical reef which has constant water changes tides and such. Given this logic although we may desire a reef replicite it would seem more successful tanks (closed system) would mimic those area in nature best suited for higher nitfrication processing. only a thought though

[grazhopr]

I have read about plenums and how to set it up. Not that I've become an expert on the subject. But now that galleon brought up an interesting remark in his article I have this question:
How any adaptation or change in the way a plenum is setup will harm the plenum functionality ? Because I have an idea running in my mind that i intended to practice in my new tank (and I haven't decided whether i'll use a plenum or a DSB yet).
Additionally, I'm not really sure how to setup a DSB...

Would something like this work?
The only variation is the space to be filled with sand that i isolate with acrilic all around the plenum (reactor area).

[Flatlander]

Hi guys. As Mike knows, I posted on a similar thread on the RAG. Figured I had better wade in here. I have posted several times before on this with Chris.

I have researched much on the use of plenums, as I was going to install it in my new tank.

As I told Mike, although the articles by Chris are very good, I still have this feeling of doubt. Some points and questions I still have.

Sprung suggests between 2mm and 5mm size for gravel. Do you agree with this Chris. I was going to use some of the GeoMarine crushed coral, but mostly the old 5mm size crushed coral we used on our undergravel systems years ago. I would think this would allow for better diffusion. However, I also wonder about the ability of the larger crushed coral to dissolve, as compared with the aragonite based GeoMarine.

I suppose my strongest belief problem, like many others, lies in the ability of the system to keep up calcium levels. Most writers, even plenum advocates, now suggest otherwise. Of course, I also have many doubts about some of their writings.

One would have to wonder why such a simple system would not be used more, by many of the advanced aquarists out there. I am sure they, as I , have no love affairs with a calcium reactor.

I can still put the system in to my new 225. I told Mike, I just had all my livestock out, to try treat the flatworms again. I could easily pull it again and install the plenum, as described by Chris. I would be a willing test subject and my experience would, IMO, limit mistakes and supply viable results and records.

I could rack any rock going in, so the gravel bed is completely open for diffusion,{a common problem}, and if dissolution of the bed does occur, it easy to replace gravel in this type system. I would also assume this would mean the use of a divider screen is out, as it would get lower as new gravel is added.

I would think my 6ft. by 2ft. footprint would be of sufficient size and the tanks 30in. height, would also assist the removal of almost 6in. of tank height.

Julian suggested, as long as most of the rock was off the bed, the amount of it does not matter as there is no conflict between the bed and the rock. This is what I would like to do, however I wonder, about the amount of calcium required to keep up the large amout of coralline growth on my Fiji rock.

Anywho, I would still need convincing before changing over.