Limitations of DSB's

[NewReefer]

In a tank that big, I'd put the DSB in the sump. There you can do whatever and still not distrub the main tank. You would need a fairly large sump for that size tank anyway right?

[SAT]

Originally posted by NewReefer
In a tank that big, I'd put the DSB in the sump. There you can do whatever and still not distrub the main tank. You would need a fairly large sump for that size tank anyway right?

You have to decide how much you believe the DSB theory. The theory states the DSB doesn't work unless it's fed enough to support a large population of critters. Putting it in the display tank usually guarantees that it's fed. Somewhere else, it may or may not be.

Putting it elsewhere also takes away one of the reasons for the DSB, which is to eliminate the need for manually removing detritus. Yes, if you have very strong current the detritus won't stick in the display tank, but how many tanks have that much current?

[NewReefer]

My LFS has a 500g tank, his sump is 300 with a DSB, been there for years. I'll have to ask what he does to keep it clean. He also uses a MUD setup, I was thinking of adding a MUD setup to my sump.

[Spanky]

Boy, you guys went all over the world.

I'll be back later, but one thing stands out.

Stop comparing closed systems to nature. They are closed systems and will operate and function as closed systems only.
Also stop thinking of DSBs as anything else but just another type of filter. When you stop thinking of them as "nature" and start thinking of them as what they really are, you'll better be able to design and maintain one.

[tdwyatt]

Originally posted by Spanky
I'll be back later, but one thing stands out.

Stop comparing closed systems to nature. They are closed systems and will operate and function as closed systems only... ...start thinking of them as what they really are, you'll better be able to design and maintain one.

thank God someone finally spoke up on this. Scott (newreefer) posted a question earlier about who had old dsb systems that was stable... I do, I had two, but have since moved the prop system to the new house. The old display is now, lemmesee, 98, 99, 2000, 2001, 2002, 2003... around 6 or so years old. It functions well, never had a problem in terms of accumulated detritis (occasional "storms " in the tank and rock to blast it out and filter it away), moderate feeding (around 1/2 oz of blender mush each two to 3 days, 3 sheets of nori a week), skimmer on again off again, circulation around 2000 gph, 180 gal tank, around 250 lbs of LR in a display tank with a 5 inch or more sand bed of mostly Aragamax (yeah, the expensive stuff) and maybe another 100 lbs of Southdown sand, seeded from who knows how many different systems (at least 15 that I can think of...) Always had RO/DI, always used IO, always had some export in the form of macroalgae or xenia, used Bionic for about 3 years, back and forth with kalkwasser and Bionic for the last 3 or so years, VHO and MH most of the time, primarily lagoonal octocorals with a few stonies and 2 tangs, a clownfish and a mandarin...

It is still ticking, I will be sampling the sandbed when it is taken down within the next few weeks for the move to the new house. I will be starting with new sand in both of the new displays and seeding them from the old sand, but for the life of me, I think that I could be using the old sand without problem. I have no scientific proof that there isn[t a problem, but I am still thinking of this as one big piece of live rock, and as such may need an occasional bath to keep it functioning (thinking in terms of years, not months). Some of the discussion here has gotten a bit out of hand as we will never be able to duplicate in the tanks the cycle of nutrients involved in gyer mechanics nor deep-sea deposition (heck, there are locations where magnesium precipitates out as near pure Magnesium metal (nodules) under the right conditions, I don't think we can approach the conditioins that are necessary to do that at the surface...

We have gotten so far from what we need to be thinking about: Closed systems with limited sinks that really become controllable compartments when considered as totally closed systems. Craig Bingman prolly said it best:

"We control what goes in, we control what comes out, in that sense, we are in total control. What we have lost is control of what happens between the addition and removal of all the nutrients of (these) systems..."

(sorry, a paraphrase of comments at MACNA XII...tdw)

I appreciate the functions that The Ocean provides for the cycling and recycling of its resources, but we only have a small portion of those functions in our tanks. As far as that goes, we still can't get many of the bryzoans , etc to survive, much less prosper from what we think we know from the surface chemistry we can study. How can we hope to use the chemistries of the whole ocean as example of how our tanks operate when we can't even tell how these things occur in totality in situ???

Speculation here without some sound backing in terms of good science is of little value in determining exactly how things work(not directed at anyone, just a comment), but it does start the process of "What if..." and "How does it do this???" If we want this to be much more than Idle discussion, it does help to have some documentation of the info, but statements like Chris's on the relatioinship for Iron to distance from shore as the limiting nutrient for algal growth is pretty much like saying that the atmosphere is mostly nitrogen, pretty much a given (check out Millero's text if there are those that really have to see it in print...). Still, much of the "facts" about sandbeds in closed systems is based on speculation and unsubstantiated claims rather that sound repeatable demonstratable science. Continuing to make data available to those that would like to study and repeat experimental observations is really the only way to see much of the hot debate on the subject subside. It will be nice to see the day when we can think of the Sandbed "secrets" in the same way we think of the atmosphere's nitrogen content.

OK, off the soapbox. The sanbed is still a substrate for filtration of nitrogen, and moving some carbon, and a parking place for some other goodies we'd like to take out with the trash. I works, prolly has a likespan in a closed system, seems to do a good job helping to feed the tank, and moves a goodly portion of problematic nutrients through our tanks without causing some unsightly blemishes when it is working well (heh, most of the time). I will try to use my logs to determin exactly how much food in retrospect has gone through the tanks, and estimate of the exports, a measurement of the stuff left in the sandbed, and I'll post what I can give as fact, and post my speculations just as that, speculatioins. Tank is as stated above, lets see what we get.

Heck, it has to come down anyway...

[NewReefer]

Thanks tdwyatt, that is exactly what I needed to hear. I'm a member of RAG for some time, but this story has been around a while. All I'm looking for is how many people has a DSB in for a long time and what do they do to keep it up! Is that too much to ask, this is probably how they extract metals and etc.. out their daily regimen. In theory is great and this seem to be the vastest subject of any reef system, if this makes since. We can only learn by doing and making mistakes and hopefully learning form them. If we also learn from those who has or had the experience then we have an advantage. The good Ol Dr. once again got things stirring, I bet he is watching all this with pride and laughter at one time.
I feel blessed to have places like this to come to and learn from others. We are all blessed because not many can do what we do and to share what we've learned in the past with others and strive to learn more and improve on what we already have, is a wonderful thing.

Hi I'm Scott T. Ardoin, new here but been around and into Marine systems for over a year now. I thought after 25 years of fresh water it was time to move up, so I did last year.

[Spanky]

Bacteria can compete with algae for inorganic nutrients, and thus may actually be a 'sink' rather than a remineralization source

Despite the fact that the corrosion processes are impeded by the formation of encrustation, metal deterioration can continue due to the presence of sulfate-reducing bacteria

In this process, the hydrogen that accumulates on the iron as a cathodic product polarizes the cathode in an oxygen-free environment. The polarization of the cathode ordinarily halts the electrochemical corrosion process. However, the utilization of hydrogen in the metabolism of the bacteria depolarizes the cathodic areas of the cell, allowing corrosion to continue unabated.
In addition, the hydrogen sulfide formed as a metabolic by-product reacts not only with iron but with all of the metals of antiquity (except gold) and accelerates the corrosion process


Tom,

check your detritus and the bacteria that are associated with it. This encrustation that's talked about is CaC03.

This is the same process that goes on in a DSB that's producing hydrogen sulfide. The bacteria are able to free up these metals and are actually using them for food. These colonies of bacteria are actually so dense that they will move pieces of metal apart and are the reason that lose metal pieces in shipwrecks are never found touching each other.

Randy missed the point and was under the impression that these bacteria needed a actual chunk of metal to work. Even though there are bacteria feeding on the metal on the surface film, what are the bacteria in line behind them feeding on? They are feeding on dead bacteria, bacterial waste, etc and the metals associated with this detritus produced by the bacteria in line in front of them. That's the process that creates these massive colonies that move metals apart. They are feeding on metals in circulation.

It's established how bacteria will drive detritus and any metals associated with it deeper into carbonate. What happens after it's been driven into a anaerobic/anoxic zone is these bacteria take over, produce the hydrogen sulfide and in turn start driving this material back out. It's a constant conga line of in and out. One type of species pushing it in and another type/s pushing it out.

[Doug1]

HEY SCOTT, WELCOME to THE REEF TANK

[MJB]

Even if we assume that anaerobic activity can result in rerelease of soluble metals into pore water etc. What is the mechanism for return to the bulk water and would they not become insoluble (whatever oxides) as they move back into aerobic areas? Can we assume that at some point available ligands are saturated and therefore these metals eventually begin to accumulate at toxic levels in the bulk water.--MJB

FWIW
You can assume that the concentration of all nutrients decrease the farther you get from coastal and upwelling areas. However, Fe enrichment experiments have been confined to certain High nutrient low chlorophyll areas of the Pacific as galleon has already pointed out. So the argument regarding Fe limitation holds true for that geographic area but does not tell the whole story. Fe limitation therefore depends on where you are and when you are there.Sorry--MJB

[NewReefer]

nice to fine another place to discuss what is going on in the reef world.

[Spanky]

Even if we assume that anaerobic activity can result in rerelease of soluble metals into pore water etc.

Nope, I'm not assuming anything. I'm just stating that as the bacterial mass increases so does your sink. All in proportion.

You can assume that the concentration of all nutrients decrease the farther you get from coastal and upwelling areas.

Again no assumption. Other than a few up-welling anomalies.

However, Fe enrichment experiments have been confined to certain High nutrient low chlorophyll areas of the Pacific as galleon has already pointed out.

The largest projects were done here. The whole CO2 sink thing.

Let's get this subject back on glass boxes gang. LOL

Would someone please read the links I posted?

[Spanky]

HEY SCOTT

I keep deep, shallow, no sand bed systems. They all work, husbandry's a little different but the result is about the same.

Forrest has a concrete casket vault down at Dynasty with about 8-10" of sand in the bottom. I know it hasn't been cleaned in 15-20 years. Does that count?

Jerel

[MJB]

Spanky,
The bacterial mass expands until the energy source is exausted and then the ecosystem collapses but we 're not talking about a finite energy source. So maybe I'm thick but I really don't see where that leads us. If the whole thing collapses OK but that harkens back to my original point. To what do we attribute this monumental collapse? Why isn't the end point of all this biological activity good old CO2 that simply outgasses like N2.
Lastly I'm not really assuming. I'm saying that the result of biological activity in anoxic /reducing areas of the bed results in release of metals. I don't see why the chemistry would be any different. But I don't see how they make their way back to the bulk water without some catastrophic event. If its via diffusion which is a very slow process then it occurs to me that you could hypothetically use water chages to reduce toxic levels of metals provided the approproiate salt mix or NSW was available.--MJB

[mojoreef]

[Spanky]

Ok now you guys have gone and done it, now I'm confused!

Mark, I thought I was saying that the metals will stay in the sand bed (or big rocks) thanks to the bacteria and associated detritus. The limiting factor, only the amount of food available to the bacteria. That not that much will be found in the CaCo3, again because of these bacteria.

Then again, maybe it's a sugar rush right now!