what is all of this dsb crash talk i read?

[Habib]

From page two of this thread:

Originally posted by Habib
IMO any sandbed is a sink for nutrients.

If there are not much nutrients (detritus or other sort of nutrients) then they cannot get in the sandbed. But if there are they will.

For example here in Holland but also many other countries we clean out the sandbed (deep beds are very scarce on the Europe except for U.K.).

When we clean it out, say every month, a lot of detritus and strongly colored water is removed.

If a nutrient poor system is what one wants then one should seriously consider a system without major non-biological sinks for nutrients.

Of course one has to remove detritus from the bare bottom and the water column and also dissolved nutrients from the water column.


IMO a sandbed is a reservoir for nutrients and acts like a buffer for such nutrients.
A buffer with very complex properties.

If the sink has become saturated the water can start to get suddenly polluted and can cause serious problems.

Compare it to a tank which really needs a skimmer to keep it low in nutrients and the skimmer stops working but is not noticed. In a matter of days or weeks the system might be heavily polluted.
Assume that there are also pumps to aerate the tank so that aeration is not the problem.

[Randy Holmes-Farley]

I agreed with that post the first time, but was too busy trying to understand Bomber's microbial extravaganza to say so.

[kwjones]

Originally posted by Bomber
A increase in water column P is a direct result of anoxic conditions. The binding of P by iron oxyhydroxides by their conversion to iron sulfides during sulfate reduction guarantees the release of P. Iron sulfides cannot bind P.

So iron oxyhydroxides bind P? Is this the reason iron based P removers like rowaphos work, or did I miss something again?

I've also noticed that when people who use macro for nutrient export can't get their macro algae to grow, it's recommended that they try dosing with iron addatives. So does macro also need a form of bio-available iron to bind P?

Kevin

[Bomber]

Randy thinks it's "vague" cause he don't know what he's looking at when he sees it. LOL Thanks Hab!

Randy, if you're having problems keeping nitrates low, then your DSB is not functioning. It's not functioning because it's full and has become a nutrient sink. One of those nutrients is P. Not only is it leaking N but also P. Your anoxic zone - the bottom one - has moved too close to the top.

From page 4

Originally posted by Bomber
Nooooo

As long as you provide habitat and food, bacteria will multiply until they either run out of habitat or food. The tricky part with these guys is they don't let go of their food until they have to and provided that they have a habitat that's malable, they will create more habitat for themselves.

ie. They will move the anaerobic area of the sand bed closer to the top.

Originally posted by Bomber
LOL you're the vent guy, you're supposed to know this.

P is manufactured in the aerobic, stored in the anaerobic. Bacterial turgor will move/push the anaerobic area up. When they run out of habitat - exposed to aerobic - they leak. It's actually a great battle zone, the anoxic/suboxic that is.

OH, nevermind. I just realized that where you work there is no aerobic zone or eutrophication.

I know we're all at work and typing at the same time, maybe we need to slow down and read.

Aerobic (needs O2) processes are not very efficient, a sand bed needs a much larger aerobic area - supported by a much more efficient anaerobic (low to no O2) area. Yours has obviously filled up. Your P sink won't work effectively because of the things I described in the anoxic (zone between the other two) and that battle zone is now leaking.
You say you're not worried about N and why should you treat P any different. You set that thing (DSB) up in the first place to totally take care on N. Why do you have N at all?
You should worry about P because, unlike N, P goes no where. It accumulates, fills your sand up, stops it from performing and doing the very thing you set it up to do in the first place. It throws off the balance between aerobic and anaerobic.


This is why you see people say, but I've been using "tap water" for X amount of time and never had a problem. Now all of a sudden I have hair algae. Tap water is water soluble highly reactive P. It's not going to sit around looking for a place to go. It's the same P you have as a end result when the sink is full - the one you test for - and - the one that would only be there leaking when the sink is full.
People get away with abusing that ability to sink P, for as long as the sink is not full.

(You're the best skeptic. )

[Bomber]

Originally posted by Randy Holmes-Farley


I agreed with that post the first time, but was too busy trying to understand Bomber's microbial extravaganza to say so.

LOL that what I meant. You're a chemist and it just totally bamboozles chemists every time. "you mean there are bugs in the way?? bugs between me and my clean chemical surfaces???" LOL

[Bomber]

Originally posted by Habib
IMO a sandbed is a reservoir for nutrients and acts like a buffer for such nutrients.
A buffer with very complex properties.

If the sink has become saturated the water can start to get suddenly polluted and can cause serious problems.

Let's get back on track. It actually easy enough to describe without having to resort to charts and diagrams and things I can't do on this thing.

Hab nailed it. All you need to understand is that bottom (anaerobic) zone is not dead. You ask the bacteria that live there to preform a function for you - denitrification. Look up those bacteria and see all the things they do. It's just that simple.
All you need to understand is the processes of denitrification and how those same processes lead to eutrophication.

[Habib]

Jerel,

IMO you were going in too much details.

[Bomber]

Originally posted by Habib
Jerel,

IMO you were going in too much details.

That's the same thing you told me! LOL I know too much about it and can't fit it all in.

[Randy Holmes-Farley]

LOL that what I meant. You're a chemist and it just totally bamboozles chemists every time. "you mean there are bugs in the way?? bugs between me and my clean chemical surfaces???"

I am involved with active programs in quorum sensing as a drug target, finding ways to get drugs through biofilms, and other issues relating to bacteria. It's not the bugs that bamboozle me, its the biologists describing sand beds.

[Bomber]

I know plus the fact that I ramble and get myself off track does not help one bit.

[Randy Holmes-Farley]

FWIW, I agree with most of what Habib wrote, so if it doesn't come along with a long of baggage on mechanistic theories that I don't believe, maybe we can call it quits and move on.

I still believe my summary as well:


"A sand bed will initially act as a sink for nutrients, both nitrogen and, to a smaller extent, phosphorus. That in itself is not a problem, and serves to keep the nutrient levels lower in the water column. After some period of time, the sand may begin to no longer be a sink for phosphorus. In some cases, about which we may debate the likelihood of it taking place in a typical reef aquarium, and under what conditions, the sand bed may even become a source of phosphorus. If the aquarium is unable to handle the phosphorus in other ways, and if it contains inhabitants susceptible to stress from elevated phosphorus (such as many calcifying corals and coralline algae), it may begin to decline in overall health."

[kwjones]

http://wilkes1.wilkes.edu/~eqc/phosphate.htm

[Bomber]

You should believe those mechanic "theories" because they have been proven and are no longer theories. The problem has been pushing the denitrification aspects in the hobby, without disclosing everything that denitirfication does.

Here's the only points where we will disagree.

A sand bed will initially act as a sink for nutrients, both nitrogen and, to a smaller extent, phosphorus.

It can be a "larger" extent just as easily. It depends on how much P you import. If you start out with dirty rocks, for instance "all that life", you can load it right from the get go. Remember water soluble P has no where else to end up. Remember in order to remove it with remote filters, you maintain a higher level in the main system - and it's going down before it goes out.

the sand bed may even become a source of phosphorus

See above. But it "will" become a source. They all do. If they didn't our Models would not work.

If the aquarium is unable to handle the phosphorus in other ways, and if it contains inhabitants susceptible to stress from elevated phosphorus (such as many calcifying corals and coralline algae), it may begin to decline in overall health."

Again, that's hedging your bets. LOL If it's no longer "sinking" and it is leaking, and you house animals susceptible to that - they will decline in overall health.

Remember, it's water soluble highly reactive P. If it's there, it's because it has no where else to go.

[G-money]

Originally posted by Randy Holmes-Farley
How do you export nitrogen?

I don't do it - I'm assuming bacteria do it for me.
I don't feed my tank amounts that require more processing than what occurs in the live rock. I can't think of any other anearobic parts of the system, so that must be where it's happening. I also skim like a madman, so I'd guess lots of stuff never even makes it that far...

The insane feeding regimen goes hand in hand with the DSB thing. I wonder if the first isn't a main reason for recommending the latter? But IME, it was always put forth that you need to feed like crazy to sustain sandbed life. How's about I just feed less and skip the middleman? No one's starving...other than the hair algae and cyano.

My feeding regimen determines my carrying capacity, not the other way around.

[SPC]

Originally posted by hillrc91
Drtango,

I understand what your saying, and it's been echoed by many others. As I told Habib, I'll take the thing out immediately if I see conclusive evidence showing that DSB's are a ticking time bomb, so to speak. I'm not too proud to admit I'm wrong, if indeed I am. But at this particular time, I've talked to many who have never had a single issue, and have been running DSB's for over a decade. In a previous thread, I stated that all of the negativity surrounding DSB's gave me a moment of pause, but with a lump in my throat, I went ahead and did it, because the balance of the evidence seems to suggest that DSB's can be a successful tool in Nitrate management.

Sorry if this has been answered in the posts following this one as I am currently reading this thread but must ask this question here. Richard, would you mind listing the "many" decade old DSB's you are speaking of here?
Steve

[SPC]

Originally posted by hillrc91
2. Have average aquarists and experts alike used the DSB method safely over a long period of time? Yes.

Ah heck, there it is again , proof please?

Steve

[Bomber]

Originally posted by SPC
Richard, would you mind listing the "many" decade old DSB's you are speaking of here?
Steve

Steve, I think you're barking up the wrong tree and here's why.

Even though denitrification leads to eutrophism, eutrophic does not mean dead. Just like there are tons of things that will not tolerate eutrophic conditions, there are tons of things that will.

While the vast majority of "reef tanks" are set up to mimic eutrophic conditions, picking and choosing - or just through a process of elimination - the animals you house in that system will still allow you to have a very successful - eutrophic reef tank.

[DonJasper]

Originally posted by Bomber
Oh sheesh, you are a chemist aren't you? This is Marine Ecology 100 minus stuff, which you never took a course in. LOL

When I have time I'll try to find something on the internet you can read.

Then I'm hoping that you should find some stuff without too much trouble. And then you'll be rid of the burden of saying "I know how it works. Trust me. Please cut me some slack - I'm not inventing this stuff."

Not that a layman like me would understand it either way!

[SPC]

Originally posted by Randy Holmes-Farley
After some period of time, the sand may begin to no longer be a sink for phosphorus. In some cases, about which we may debate the likelihood of it taking place in a typical reef aquarium, and under what conditions, the sand bed may even become a source of phosphorus.

Hi Randy,

Can you explain the "may" portion of this? What would be the factor that could lead you to believe that there is a "may" in this case?

Originally posted by Bomber
Steve, I think you're barking up the wrong tree and here's why.

Even though denitrification leads to eutrophism, eutrophic does not mean dead. Just like there are tons of things that will not tolerate eutrophic conditions, there are tons of things that will.

While the vast majority of "reef tanks" are set up to mimic eutrophic conditions, picking and choosing - or just through a process of elimination - the animals you house in that system will still allow you to have a very successful - eutrophic reef tank.

I understand what you are saying here, Jerel, some find hair algae to be a natural part of a reef system that houses non SPS type corals. Hmmmm, I wonder though, in Dr Ron's case he had a complete tank "crash" after 4 years in his DSB tank. If this "crash" (crash meaning animals actually died) happened to be caused from an organic build up in his system (as opposed to heavy metal poisoning like he claims), then maybe even a "successful" eutropic reef tank could be questioned in some cases.
Steve

[Randy Holmes-Farley]

Can you explain the "may" portion of this? What would be the factor that could lead you to believe that there is a "may" in this case?

Which one?

"After some period of time, the sand may begin to no longer be a sink for phosphorus."

When no one has ever shown that it is a substantial sink in a normal reef aquarium (much less every reef aquarium operated under any ordinary conditions), I allow for the fact that it may not always be a sink, and hence may never "stop".

Also, some folks clean their sand, some periodically replace parts of it. Some use silica sand. Some use aragonite. Would phosphate accumulate in both? Some may have organisms that regularly ingest it and clean parts of it, leaving it open for more phosphate to enter. Some may slowly accumulate detritus more and more every day, again not "stopping" accumulation.

All of these are possible reasons why sand may not "stop" being a sink for phosphate. Some of these cannot go on forever (although some can), but reef aquaria have lives for other reasons. If the tank has a life of 5 years, and it takes 8 years for a sand bed to stop accumulating phosphorus, few aquarists would be concerned.


"the sand bed may even become a source of phosphorus"

For this "may", I'm even more unclear about when and how this might happen (or not). So I think "may" is the best description. Part of the uncertainty also relates to whether one is talking about total phosphorus, or free phosphate, or something in between. I don't see a clear reason why a sand bed must become a source of total phosphorus (which is quite different than no longer being a significant sink).

[threeheaddog]

so do you flush the dsb or not?

how often?

if not then what to do when full?

reefs have storms.
should we give our dsb's "storms"

i give my 1" main bed "storms" every 3 months with a 20% water change and leave my 6" dsb alone in sump. is this ok?

do i need to add more sand to main bed?

[TurboRook]

Correct me if I'm wrong, but isn't this the method by which the action of anaerobic bacteria would release phophates back into the water column?

[Randy Holmes-Farley]

That is how phosphate is released from organics in an anaerobic fashion, yes. A similar process can happen aerobically and release the same amount of phosphate. I show the aerobic version in this article:

http://www.advancedaquarist.com/issu...t2003/chem.htm

No one questions that when organics are degraded, phosphorus and nitrogen must be released.

I see they make similar claims to Bomber about iron oxide hydroxide becoming iron sulfide and no longer binding phosphate. I agree that can happen, but I do not believe there is enough iron in our sand beds for this to cause a sudden crash.

The reference justifying that claim is titled :"Phosphate mobilization in iron-rich anaerobic sediments: microbial Fe(iii) oxide reduction versus iron-sulphide formation. "

I wouldn't call aragonite, iron-rich.

[Randy Holmes-Farley]

Here's the full abstract of that reference:
Phosphate mobilization in iron-rich anaerobic sediments. Microbial Fe(III) oxide reduction versus iron-sulfide formation. Roden, Eric E.; Edmonds, Jennifer W.. Dep. Biological Sciences, Univ. Alabama, Tuscaloosa, AL, USA. Archiv fuer Hydrobiologie (1997), 139(3), 347-378.

Abstract

Mechanisms of PO4 mobilization and retention were examd. in Fe-rich anaerobic freshwater wetland, lake, and coastal marine sediments. Direct microbial Fe2O3 redn. solubilized only 3-25% of the initial solid-phase PO4 during incubation expts. with SO4-free sediment. Expts. with reduced, non-sulfidic Fe(II)-rich sediment demonstrated PO4 sorption by the solid phase, and chem. equil. calcns. indicated that conditions were favorable for the pptn. of Fe(II)-PO4 minerals, e.g. Fe3(PO4)2. Much of the PO4 released during microbial Fe2O3 redn. was captured as Fe(II) compds. Enhanced PO4 liberation to sediment pore waters (33-100% of initial solid-phase PO4) occurred during anaerobic incubation in the presence of abundant SO4 and was directly correlated with SO4 redn. and FeS mineral formation. Incubation of PO4-amended sediment with different amts. of SO4 demonstrated a linear correlation between PO4 release and SO4 redn. Release of PO4 to sediment pore waters during decompn. of fresh org. matter (freeze-dried cyanobacteria) was more extensive in SO4-amended (67% of added org. P) than in SO4-free sediment (17% of added org. P), and the ratio of dissolved PO4 released to org. C oxidized was 7-fold higher in SO4-amended sediment despite a common level of overall org. C and P mineralization in both treatments.

[Randy Holmes-Farley]

If that sort of mechanism is the basis of the concern about phosphate being stored and then released, then I think it is faulty for our aragonite and silicate sand beds.

It is a stochiometric storage of phosphate as iron phosphates (one iron to one phosphate, roughly). I do not believe that there is enough iron in our reef systems to make those same types of precipitate become an important tissue that might later come back to haunt us.

Now folks using mud systems... that's another story.