Weekly Discussion - BB vs DSB

[Anonymous]

Weekly Discussion - BB vs DSB

There have been discussions about these two methods for the last year or so. What do you think of them, why, and why do you think of the process of discussion?

About the RDO Weekly Discussion:
This discussion is meant to get at your experience and to share information that is in your head, so don't necessarily treat it as information gathering. State your opinion and, if available, use material, anecdotal or otherwise, that will back up your opinion.
Past weekly discussions will be archived in the archives.
If you have topics that you think would be helpful for the RDO community to discuss, please send me a pm or start your own thread! :mrgreen:

 

[Len]

I'm gonna kick this off by saying I have a 9 year old DSB and I have yet to encounter problems with it. I have rarely done water changes and have only minimally vacuumed the substrate bed once (about 5 years ago).

I've been in this hobby during (and before) BB was the methodology de jour, and from my personal experience, DSB tanks I've operated all have looked significantly healthier then BB tanks I've husbanded.

People's mileage may vary.

 

[Anonymous]

Until someone does a test with two identical tanks, with the only variation being DSB and BB in which they are run for several years, this will boil down to mostly opinion. Anecdotal evidence is not useless, most of what we do to (successfully) keep reefs is based on it. But this seems like a difficult one to solve.

For myself, I don't find the DSB nay-sayers persuasive, and have a (3-4 inch) sand bed in my reef.

 

[npaden]

IMO some of the arguments for BB don't really hold up. One of the latest agruments I've seen is that since most researchers setup BB tanks that we should. Well most researchers have the tank setup for just a short time for a specific expirement. Also having sand would just put an unnecessary variable into the mix on their research.

I think people always want to find something to blame tank problems on so it isn't their fault. The current scapegoat is DSBs. If you have algae or your corals aren't growing very fast or if you have a power outage and some fish die it was the DSBs fault.

In a few years when a bunch of people have switched to BB and still have algae problems and their corals aren't growing very fast and they have a power outage and they lose some fish they will find something else to blame it on.

My 2 cents.

 

[Anonymous]

I have to agree with the above comments. As some of you may recall, I posted several threads documenting a serious algae problem that I had during the past year in a relatively new 400g reef tank with a 5" DSB. The problems that I believe led to the algae problem have been corrected and the problem has been resolved, although it took me 7 months to do it. I did not remove or even touch my DSB.

The anti-sandbedders would most likely have told me that my algae problems were due to the DSB. And many would have given up and yanked the DSB long before I did. But I stuck it out and have demonstrated that the DSB, at least in my tank, was not the problem. I am convinced that I will have a more complete eco-system and healthier tank in the long run as a result of keeping the DSB.

FWIW, I have a DSB in a FOWLR tank that is home to some big eaters (morays and triggers), and which I believe helps to keep my nitrates in check.

 

[Anonymous]

Milz, could you breifly recount what was the algae problem in your tank?

 

[Anonymous]

Righty, I can't believe I'm taking the bait

Until someone does a test with two identical tanks, with the only variation being DSB and BB in which they are run for several years

The bottom line is that closed system models have demonstrated over and over again that phosphorous release does occur from a sediment sink. It’s better than anecdotal, too: it’s peer reviewed and a victim of the scientific process. Better yet, this information is easily obtainable in any marine chemistry textbook.

IMO some of the arguments for BB don't really hold up. One of the latest agruments I've seen is that since most researchers setup BB tanks that we should. Well most researchers have the tank setup for just a short time for a specific expirement. Also having sand would just put an unnecessary variable into the mix on their research.

Foremost, the length of time specimens are being observed has absolutely no bearing on how long the system they are being observed in is run. Secondly, there are many long-term projects that grow corals in closed systems for recruitment and replenishment experiments/research. And finally, many short-term setups for experiments do indeed use sand. Dr. Jaubert’s Microcean was ultimately developed and patented for just this purpose, despite the longevity of his original system tests.

Now, give me another argument that doesn’t hold up, in your opinion.

The anti-sandbedders would most likely have told me that my algae problems were due to the DSB.

I have no doubt that it was thanks to establishment of different phosphorous pathways in the sandbed, liverock, wherever. Your pathways got established, bacteria took over, and your bed started to sink just like it is supposed to. Just like in nature.

I am convinced that I will have a more complete eco-system and healthier tank in the long run as a result of keeping the DSB.

Explain to me, how does keeping a nutrient that is toxic to most scleractinians and limiting to nuisance algae in the system where these scleractinians are the target organisms make any sense whatsoever? It’s not a healthy or complete ecosystem, it’s poor husbandry.

Some realize this, and still like their sandbed. More power to them. What do they do? Take precautions against it sinking the toxin long term.

 

[Anonymous]

Milz, could you breifly recount what was the algae problem in your tank?

My 400g tank is about 18 months old, although the live rock and much of the live sand has been with me for much longer.

Last April, following a 3 week trip to South America, my tank started to experience cyno problems. Prior to that, the tank was healthy and stable. The reason for the problem was immediately identified, although I suspected that he had something to do with feeding changes that may have occurred while I was away.

Hair algae quickly followed on the heels of the cyno. Hard corals started dieing off.

In response, I cut back on feeding, replaced my MH bulbs, added carbon, replaced DI cartridges, increased skimmer cleaning frequency, etc, etc. - no change.

I then started checking my water supply. After purchasing a TDS meter, I was shocked to discover that my RO membrane, which was less than a year old, had gone bad. This failure led to a premature failure of my DI cartridge. Best as I can guess, the RO failure was the result of something called membrane creep (repeated, short-term cycling) that was caused by leaving the RO unit hooked up to my sump for continuous auto-top-off.

I also had a calcium reactor that was not working properly do to a change in media that quickly clogged up the sponges inside the unit, thereby drastically reduce internal turn-over rate. This, in combination with a bad Calcium test kit, resulted in depressed calcium levels in the tank. Both of these problems were not apparent or discovered until I obtained additional test kits to double check the water parameters.

Anyways, the tank is big so problems take a long time to manifest themselves in an identifiable manner. Likewise, ridding the tank of problems (like phosphates and nutrients absorb by the DSB and the live rock) also takes a long time.

 

[Anonymous]

Galleon, the point that I was trying to make and which you may have missed is this:

If my sandbed was in fact the source of my algae problems, then why have my algae problems been resolved without altering or removing my sandbed? If, as you opined, my sandbed started to "sink", then has it now "un-sunk"?

In any event, my observations were that my sandbed had little to do with my algae problems even though most of the anti-sandbedders would have been quick to point to the sandbed as the source of the problem.

But please understand, I am not saying that sandbeds cannot be a problem. To the contrary, I am sure that they can be (although not necessarily will be). I am merely pointing out that many who claim to have problems because of their sandbed may be incorrect, and that we must be careful of drawing conclusions from such observations.

The bottom line:

I have a DSB. I had an algae problem. My observations indicate that the algae problem was unrelated to the sandbed. Will my DSB ever be a problem? I don't know.

 

[Anonymous]

Righty, I can't believe I'm taking the bait

I am thrilled you took it. Its nice to have someone who studies this stuff talk about it.

Milz,

The perhaps the phosphorous sinking pathways were not established, so the phosphorous from your faulty RODI did not get sunk. Over time, they did get established, and the phosphorous did sink, and the problem went away.

The issue at had is, how/if/when will the bed fill, and how/if/when it will re-release. To this there doesn't seem to be a good answer.



The worst thing about this on going discussion (not this thread, nothing wrong with this thread) is that some of the BB people have gotten just as one sidedly vocal about BB as they claim some of the DSB people have. I am amazed that the polarization was so swift.

Here is what I think it all boils down to:
Bad things (phosphate release, sulfide release) can happen in sand beds, we just don't know how fast they can happen.
We are not sure if you can mitigate them, but it seems like you should be able too.

The other thing I think is important in this ongoing discussion is that there are different kinds of sand beds, and 'DSB' doesn't describe them well, nor does is describe the way all the systems with sand beds are maintained.

 

[playfair]

ghostofmilz, your tank is too young to have the associated problems caused from old sand beds.

I agree that we look for a scapegoat, because it's easy. Aren't the same people that are SO against DSB's now the same ones against all other methods a few years ago?!

How many people mechanically filter their tank water? I've read time again how bad filter pads are and suspect most people don't use them... Surely allowing "junk" to stay in the tank to magically be processed has accelerated any long term sandbed problems, as it would with liverock problems as well.

My tank is nearing 5 years, and has had it's share of OTS. Can't blame it on the sand as what little I have stays mixed from my Tiger Pistol. So what then? We add all kinds of stuff to the water, with the hope that it gets "used up" or breaks down to something harmless, but all we are really doing is putting off the inevitable on whatever denitrification system we employ. How long it takes for problems to show up depends on how hard we push the system. I see many DSB problems stemming from the crowd that doesn't filter and brags about how heavilly they feed their tank. I suspect similar problems will show again with BB unless the "total package" of husbandry is modified.

 

[Anonymous]

The bottom line is that closed system models have demonstrated over and over again that phosphorous release does occur from a sediment sink. It’s better than anecdotal, too: it’s peer reviewed and a victim of the scientific process. Better yet, this information is easily obtainable in any marine chemistry textbook.

The sediment sinks described in the above models; how similar are they to a typical reef aquarium DSB and in what ways do they differ?

 

[Anonymous]

I have no doubt that it was thanks to establishment of different phosphorous pathways in the sandbed, liverock, wherever. Your pathways got established, bacteria took over, and your bed started to sink just like it is supposed to. Just like in nature.

....

Explain to me, how does keeping a nutrient that is toxic to most scleractinians and limiting to nuisance algae in the system where these scleractinians are the target organisms make any sense whatsoever? It’s not a healthy or complete ecosystem, it’s poor husbandry.

Ignoring the "poor husbandry" crack, could you please elaborate on the above. The analysis/argument appears to have come from a discussion that took place elsewhere.

 

[Anonymous]

Ignoring the "poor husbandry" crack

It's no crack. It is poor husbandry. You are keeping nuisance algae fertilizer and coral poison (phosphorous) fluxing in a portion of the water column just below where it could be used by algae and affect corals. What logically do you think would happen if you let it build up? Eventually it's not going stay confined to that lower layer of water when that lower layer's volume becomes saturated and the free phosphate being fluxed into and out of the water column is now in a photic area of your tank.

The analysis/argument appears to have come from a discussion that took place elsewhere.

No. I've been, for the most part, riding the pine pony on these debates "elsewhere" for a while now, thanks to the content most of them had devolved to. I'd like to keep the same from happening to this discussion, and I'm sure there are others that agree.

As for elaboration of what was not addressed above: It takes a little while and several species successions (ie, algae took over, then died out) to establish the most efficient climax pathways for phosphorous. It is a limiting nutrient, so it's highly prized and competed for.

The sediment sinks described in the above models; how similar are they to a typical reef aquarium DSB and in what ways do they differ?

Good question Dan. The similarities are fundamental, and the differences are superfluous for the most part.

The similarities are the inputs, the infauna and epifaunal critters, the processes in the sandbed, the sinking of particulates and organics in the sediment, low chemical and physical exports.

The differences are the input amounts, sediment grain sizes and sediment type. Many experiments use several types and sizes, and measure rates of release from each, etc. The other differences would be specific biota and aquarist interference (fish digging, aquarists digging, etc.), which would indeed affect the release rates.

The models run to investigate the eutrophication of Florida Bay were/are run almost identical, as far as I know, to a "Dr. Ron" style DSB.

If you want something more comparable to coral reef biotopes: we also know that regeneration of phosphorous from reef substrate is what allows any reef algae to grow, as healthy reef water is too phosphate-limited to feed it. On a typical, "healthy" reef, most organic matter is exported. The small amounts that remain and get trapped in substrate are regenerated into trace amounts of usable phosphates, just enough for the benthic algae that dominates healthy reefs to snatch up.

The reefs where algae overgrowth is becoming a problem are the same reefs where lack of significant flushing is becoming a problem, or, more input is being made than what the flushing can compensate for. You get more and more phosphate being regenerated by benthic biota, and you get a succession in favor of algae that are no longer limited in their growth.

 

[Jolieve]

Both methods have their merits from what I have seen, but I have yet to see any evidence that compells me to remove my dsb. There are many conversations available, discussing theories, but I want to see a study done on both with proven benefits of going bb before I will consider removing my dsb seriously.

That said, I have had algae problems out the wahzoo since August. At that point, the dsb was only a month old. I would think that the fact that I live downstream from the largest phosphorous mine in North America and started my tank with tap water, would have more to do with the phosphate content in my system than my dsb.

J.

 

[Anonymous]

It's no crack. It is poor husbandry.

This appears to be an opinion disguised as a fact. You must be a college student. :wink: only teasing

On a typical, "healthy" reef, most organic matter is exported.

Through what mechanisms and how do they or might they differ from those in our reef tanks?

The small amounts that remain and get trapped in substrate are regenerated into trace amounts of usable phosphates, just enough for the benthic algae that dominates healthy reefs to snatch up.

Is it your opinion that this process is not possible in our reef tanks? If so, why?

BTW, I am not arguing with your assertions. From my perspective, the goal should be to duplicate the natural healthy reef that you have described. Is it your opinion that certain aspects of a natural reef (eg, benthic algae populations) are not possible to achieve in the relatively closed system of our reef tanks? More specifically, is it your opinion that it is impossible to establish a sandbed that mirrors the sandbeds surrounding natural reefs? If so, why?

Thanks in advance for your input.

 

[Anonymous]

From:

Kamatani, A,; Amano, M. 1984. Phosphate and silica regeneration from fecal pellets of benthic animals collected from Tokyo Bay. BULL. JAP. SOC. SCI. FISH./NISSUISHI., vol. 50, no. 6, pp. 999-1003

"The study strongly supports the assumption that phosphate and silica regenerated from the fecal pellets supply a significant fraction of nutrients required by primary producers in the water column during summer months when anoxic conditions are spreading in the water-sediment interface."

In other words, phosphate is regerated your benthic biota when the anoxic band nears the surface of the bed, moves into the bulk water and feeds nuisance algae.
-----------------------------
From:

Ikeda, T; Carleton, JH; Mitchell, AW; Dixon, P. 1982. Ammonia and phosphate excretion by zooplankton from the inshore waters of the Great Barrier Reef. II. Their in situ contributions to nutrient regeneration. AUST. J. MAR. FRESHWAT. RES., vol. 33, no. 4, pp. 683-698.

"Calculations from an empirical equation relating temperature to oxygen consumption by a bottom community indicated a high potential for benthic nutrient regeneration in reef inshore waters (27 multiplied by 1 g m super(-2) per year, as nitrogen). The bottom community therefore appears to be the most important source of nutrient regeneration within the area studied."

Demonstrates importance of regeneration of phosphate by substrate for algal growth.
-----------------------------
From:

Fan, C-X; Zhang, L; Qu, W-C. 2001. Lake sediment resuspension and caused phosphate release--a simulation study. Journal of Environmental Sciences (China). Vol. 13, no. 4, pp. 406-410.

"The internal phosphorus loading induced by resuspension is estimated to be 8 - 10 times greater than the release from undisturbed sediment."

Now do you really want to stir that bed?
-----------------------------
From:

Hasnaoui, M; Kassila, J; Loudiki, M; Droussi, M; Balvay, G; Barroin, G. 2001. Phosphate release at the water-sediment interface in a fisheries pond of the Deroua fish farm (Beni Mellal, Morocco). Revue des Sciences de l'Eau/Journal of Water Science [Rev. Sci. Eau/J. Water Sci.]. Vol. 14, no. 3, pp. 307-322.

"The phosphate (P) released from the sediment is the essential source of P for phytoplankton when the ponds are not fertilised"

Speaks for itself.
-----------------------------
Abstract from:

Gomez, E; Fillit, M; Ximenes, MC; Picot, B. 1998. Phosphate mobility at the sediment-water interface of a Mediterranean lagoon (Etang du Mejean), seasonal phosphate variation. Hydrobiologia [Hydrobiologia]. Vol. 373-374, no. 1-3, pp. 203-216.

"The Mejean Lagoon (Herault, France) is a confined, shallow system, 0.7 m in depth, with a surface area of 747 ha. Its sediments have a fine granulometry and are evenly distributed. The bathymetry and hydrodynamic behaviour of the basin create two zones with restricted exchanges between them. The western part (60% of the total surface area) is rich in dissolved phosphate (> 1 mg l super(-1) in summer) and receives the majority of the phosphate (P) inputs from the watershed. The heavy macroalgal population consists of Gracilaria throughout the year and Ulva in summer and autumn. Phytoplankton levels sometimes reach 100 mu g l super(-1) of chlorophyll a. The sediment-water phosphate exchange varies with environmental conditions and macroalgal growth. P mobility was studied on the basis of these characteristics. Algal biomass and water characteristics were measured at 15-day intervals throughout 1993. A seasonal study was conducted in 1994 to investigate which P fractions in the sediment were involved in the exchanges. The springtime rise in temperature reactivated decomposition of the macroalgal biomass that had accumulated in autumn. The redox potential (E sub(H)) fell as a result of this biological activity, leading to a decrease in the inorganic P fractions. This P release accounts for the higher P water concentrations observed in the lagoon in summer. The mobility of P fractions shows that the P stored in the sediments plays an active role in the dynamics of the overlying water. Seasonal variations in these fractions explain the patterns of P storage and mobilization."

So, while there are controlling factors as to rate of release (and there a lot more than just the temperature control that this article subscribes to), there is constants flux at the water/sediment interface.
-----------------------------
Abstract from:

Valdes, D; Real, E. 1998. Ammonium, nitrite, nitrate and phosphate fluxes across the sediment-water interface in a tropical lagoon. Ciencias marinas. Ensenada [CIENC. MAR.], vol. 20, no. 1, pp. 65-80.

"The sediments of Chelem Lagoon, on the coast of the Gulf of Mexico, north of the Yucatan Peninsula, were studied measuring the nutrient concentrations in the interstitial water. The average values were: ammonium 459 plus or minus 281 mu M, peaking up to 1,045 mu M; nitrite 1.8 plus or minus 1.8 mu M, with a maximum of 5.3 mu M; nitrate 8.2 plus or minus 10.3 mu M, reaching 34.7 mu M; phosphate 0.4 plus or minus 0.4 mu M, with a maximum of 1.1 mu M. Fluxes were estimated with Fick's first law equation. In all cases, the mean flux of the 14 samples from the lagoon were from the sediment to the water column; these values were 182 mu mol/m super(2)h for ammonium, 0.5 mu mol/m super(2)h for nitrite, 1.9 mu mol/mu2h for nitrate and 0.03 mu mol/m super(2)h for phosphate."

Lots of nutrients in the porewater. What is keeping your sediment's porewater from building up those kinds of concentrations?
-----------------------------
From:

Nakamura, Y. 1994. Effect of flow velocity on phosphate release from sediment. Water Science & Technology [WATER SCI. TECHNOL.], vol. 30, no. 10.

"At very low flow velocities, transport through the diffusive boundary layer is the limiting factor...and phosphate release rate is expressed as a linear decreasing function of the velocity. When flow velocities are increased... phosphate release rate become independent of velocity, since the reactions in the sediment are the rate limiting factor. "

So with the high flows in reef tank, the liberation reactions are firing off as fast as they can.
-----------------------------

Enough for now.

 

[REEFKEEPA]

Good Lord, How complicated does this subject have to be? Everyone has an opinion and a preference. If you remove all of the hypothisis and speculation it all comes down to personal preference.What looks best?
IMO DSB.

 

[Anonymous]

Thanks for the info. I only skimmed it and I will have to read it in more detail later.

But I was still looking for your bottom line opinion - Is it possible to create a viable DSB in a reef aquaria? Intiutively, I would opine that although difficult, it should still be possible.

 

[Anonymous]

Tokyo Bay

inshore waters of the Great Barrier Reef

Lake sediment

fisheries pond

a Mediterranean lagoon

tropical lagoon

Not to belabor this, but there seems like a lot of variety in those substrates, although I guess you could say that proves your point. But some of those situations such as tropical inshore water (mangrove) and lakebeds contain considerable plant detritus as part of their makeup.

An aquarium DSB is very fine, and closed to big chunks of crap. What gets down there is probably just fecal matter from benthic and filter feeders. Just wondering about the differences. I have dug in some inshore waters, and man they sure ain't like my DSB. Stinky!!!