what is all of this dsb crash talk i read?

[Flatlander]

[i]
You would be driven out of your house by the smell long before it did any damage to your tank. [/B]

My wife will swear to that.

[Randy Holmes-Farley]

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.

This is all just part of the denitrification process. It's where you got your hydrogen sulfide from.

All these things are just part of the denitrification process. You can't have one without the other, and having one - guarantees that you have them all.


Still confused. Are you talking about a situation where someone adds an iron-based phosphate binder?

Otherwise, I don't see where all the iron oxide comes from to begin with.

If yes, I don't see it being in the low oxygen regons to become iron sulfide.

[Bomber]

It's taking place in that very thin line between aerobic and anaerobic - anoxic. It takes very little, it's cycled. You have more than enough.

[Randy Holmes-Farley]

You are claiming that in aragonite sand beds, that the phosphate is stored initially and happily as iron phosphate, and then when sulfide comes along the iron forms iron sulfide, releasing phosphate?

[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.

Go back to the top of the sand bed and start over. That's where it's introduced. Incorporated into bacteria, moved down, played with, and then tossed back up by the anoxic processes. If it's not needed in the aerobic area, it's tossed out. If it is needed, it just starts all over again.
When the "sink" is full, it's not needed and tossed out.

It's that simple.

BTW I'm not claiming anything. That was a direct quote from your buddy Frank Millero. I just wanted to see what you would say about it. LOL

[Atoller]

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.

Go back to the top of the sand bed and start over. That's where it's introduced. Incorporated into bacteria, moved down, played with, and then tossed back up by the anoxic processes. If it's not needed in the aerobic area, it's tossed out. If it is needed, it just starts all over again.
When the "sink" is full, it's not needed and tossed out.

How about some formulas? We care about how these processes work. How the bacteria put these reactions together. We don't care to take your word for it that they're "there" and that's what they "do" .

[Bomber]

Acutally I was hoping that you would do it.

I'm the biologist, I just know "who" does it. LOL

[Atoller]

Acutally I was hoping that you would do it.

You suck.

So I take it I am just talking about the lithotrophs and ignoring the bacteria that generate H2S from organic matter?

[Bomber]

Let's see what you got out of all that grant money this year.

[Atoller]

That grant money was to work out partition coefficients in fossils, LOL.

So, first of all, Sulfidogenic bacteria require anaerobic habitat. Since the ocean usually ensures most species are in their most oxidized form (a la sulfate), sulfate is the most acceptable/common proton acceptor for sulfur-reducers. (Although there are those that use elemental sulfer, and they come in pretty handy in autotrophic denitrification in wastewater treatment).

Basically, sulfate doesn't make such a hot electron donor. So, it becoems activated by the enzyme ATP -sulfurylase. The product is APS. APS is converted to bisulfite and AMP, then the bisulfite acts as the acceptor and, through a series of reductions, is converted to Hydrogen sulfide.

The highly simplified version is:
APS + 2e --> AMP + HSO3-
HSO3- + 6e -->H2S

Autotrophic denitrification is another cool process that also uses sulfur, but in this case the nitrate is reduced. Nitrogen, oxygen, sulfate and carbohydrate molecules as well as protons are the final product.

[Bomber]

Originally posted by Randy Holmes-Farley
You are claiming that in aragonite sand beds, that the phosphate is stored initially and happily as iron phosphate, and then when sulfide comes along the iron forms iron sulfide, releasing phosphate?

Randy and I are both getting old. Just give him the short answer before we lose him.

[photobarry]

Yeah, I think Atoller made most of that up!

[Atoller]

Sheesh, and you guys yell at me for asking to get to the point LOL.

I think what Bomber is prodding me to post is something to this tune: autotrophic denitrification generates sulfate, the sulfidogenic bacteria convert that to hydrogen sulfide, the hydrogen sulfide makes metal sulfides (which robs the ferric iron from the iron oxyhydroxide with phosphate in tow), releasing phosphate. Don't forget, bacterial adsorption will tend to concentrate the phosphate-enriched iron oxyhydroxides.

[Bomber]

That's it.

Now Randy will ask you where all this iron comes from, you will explain to him that it takes very little because of where this process takes place

and then I will explain how that's not the only way P is released and we'll have a discussion about pH.

When that's over, I'll bring up salinity and micro-environments and explain how they also facilitate and mobilize the release of P

Then we can all wrap it and show what a slippery slope this really is and that it's truly a miracle of nature that we're not all up to our eyeballs in P.

[photobarry]

Originally posted by Bomber
Then we can all wrap it and show what a slippery slope this really is and that it's truly a miracle of nature that we're not all up to our eyeballs in P.

The technical term is "guano". And I'm glad we're not up to our eyeballs in it! Yuck!!

[Bomber]

Here it goes folks. It's been way over a year. Someone post something, anything that proves me wrong.
Look it up, learn something.

and in the mean time - I'm going diving.

[Randy Holmes-Farley]

Explain it to me one more time.

I say DSB's leak phosphates.

You say they leak hydrogen sulfide.

Ron says they leak heavy metals.

The benefits are what again? I forget.

All nutrient export methods have drawbacks, as far as I know. You take your poision, and live with the results.

[Randy Holmes-Farley]

Frankly, I think I'm being bamboozled.

I don't see enough iron being present to bind enough phosphate in this iron phosphate reservoir to be important.

You are claiming that is just waiting until one day the sulfide that results in anoxic regions reverses the flow of phosphorus from water to sediment to become sediment to water. And that that reversed flow is so great that it causes a tank crash.

Yes, I do ask where all that iron comes from, and not seeing an adequate answer, I suspect the theory is lacking.

Here it goes folks. It's been way over a year. Someone post something, anything that proves me wrong.
Look it up, learn something.


Since I am playing the role of the skeptic, and not the crusader, I don't feel that I need to prove anything. You may be right, but I remain unconvinced that sand beds do the things that you claim, and that doing so, cause what most reef aquarists refer to as tank crashes that they all fear.

[photobarry]

The iron is recycled from the oxidized to the reduced form. It doesn't go anywhere and actually slowly accumulates as the bacterial population increases. At least, that's my understanding of things.

[Randy Holmes-Farley]

1. And where is the phosphate being stored, while it watches this small amount of iron cycling around?

2. When the iron becomes iron sulfide in Bomber's hypothesis, why can't the phosphate continue to reside where it is in "1"?

[photobarry]

I believe that the phosphate is stored in the anoxic part of the sandbed. This zone continually increases in size until the majority of the sandbed in anoxic. At that point, the only place to go is up and out of the sandbed. Basically, it brings the phosphate in contact with the photic zone.

[G-money]

Sorry, I have to comment...

The big benefit of DSB's seems to be nitrate reduction??? Please.
My tank (no sand) has never tested for as much as 1 ppm of NO3 - ever. There are organisms that grow right in your tank that can pull nitrogen out of the air...let them try that with phosphate.

I'm not worried about nitrate in the least. It takes a lot of nitrate without phosphate to hurt much of anything. Nitrate-phobia is one of those myths that needs to go away...along with the thought that one needs a DSB to nil their NO3. You have to have some serious system design flaws or poor husbandry practices (sorry) if you find yourself unable to keep the level low... What was that about falling off a log?

[Randy Holmes-Farley]

I believe that the phosphate is stored in the anoxic part of the sandbed. This zone continually increases in size until the majority of the sandbed in anoxic. At that point, the only place to go is up and out of the sandbed. Basically, it brings the phosphate in contact with the photic zone.

Stopping the continued accural of phosphate wouldn't seem much of a problem. Somewhat like a bare bottom from day one.

I'm not worried about nitrate in the least.

You may not be, but others are trying their best and are still having trouble managing nitrate. I had elevated nitrate for years before adding a sand bed and macroalgae.

How do you export nitrogen?

[gregt]

Stopping the continued accural of phosphate wouldn't seem much of a problem. Somewhat like a bare bottom from day one.

Yes, but mostly no. A sandbed is going to capture the detritus and prevent you from removing it. That's the ONLY reason I have a BB tank. With BB I can increase flow so the detritus is kept in suspension and can be removed by my skimmer before it breaks down and can be stored anywhere inside my system. If I drop an astrea snail on one side of my tank it won't stop rolling around until it laps the entire tank at least once. If I put sand in that tank you wouldn't be able to see 2" past the glass.

[Randy Holmes-Farley]

Yes, that is a good point. It is a possible reason to avoid sand beds from the beginning. But it wouldn't seem to me to be something that will click in one day 4 years after setting up the tank.

I don't doubt that many sand beds may be detritus traps, and may help elevate tank phosphate for that reason. If Bomber made that claim on thread one as the basis for the concern (instead of this vaguely defined process involving every known biological activity in sand beds ) , then maybe we could have spent the last hundred posts solving some other problem.

It also provides an action that aquarists may consider: monitor phosphorus in teh water column. If it isn't elevated (and you are not experiencing an algae bloom) then the sand bed is not likely doing anything bad (by this mechanism, anyway).

If it is elevated, then the sand is one thing to examine as a possible concern.