DSB...Let's Discuss!

[NaH2O]

With less critters, would the sand bed be fully functioning? I guess there would be enough life to keep things moving in it *(thinking out loud)*. Scott, I'm following what you are saying, I'm just trying to get a handle on this so I get the most out of my system by understanding it.

 

[Cougra]

Originally posted by NaH2O
Michelle, do you have any ideas on what was causing the tank crash?...maybe the CC?

That was part of the reason! I didn't know much about setting up tanks when I first set this one up. I think I basically had way too much detritus build-up under all the CC despite attempting to keep it clean. It reached a point where the system couldn’t handle the load anymore and started to through off my water chemistry.

When problems first started in the form a small cyano outbreak, I figured that my lighting needed to be changed; when that didn’t work I tried reducing photoperiods and increasing water circulation, followed by reduced feedings and frequent water changes. I removed some of the bioload and put them into separate small tanks and added some more caulerpa and thing continued to get worse instead of better. Hair algae slowly took over my tank and despite all this extra growth in algae/cyano I STILL had nitrate readings in the tank. I knew I needed to do something drastic and changing the substrate was the next course of action.

I read about a lot of people having problems with their tanks crashing and faced the reality my tank could be considered one of them.

Originally posted by mojoreef
I was wondering why the replacement of sand?? I am not sure I follow this.

Mike

Mike:

My primary reason for changing out a bit of sand constantly stems from what I’ve seen with my previous substrate. The tendency of detritus to fall to the bottom and eventually pollutes the system. I’ve tore down a few tanks in the past and have always found that the bottom of the tank had the same disgusting sludge that reeks to high heaven! (Similar to what we were talking about in the plenum discussion.) I want to remove as much of that detritus as possible to help prolong the life of the sandbed.

I can’t really figure out a way to get rid of this sludge at the bottom of the tank without removing the sand as well. Thus I found the concept of having a plumbed system under the plenum a very interesting concept and could see some potential for it.

Originally posted by mojoreef
The clumping is cause by hard water (which we want) with the lack of stiring, in the case of DSB's by bugs I guess.

I realise that the critters in the sand are suppose to do this for you and if you have an adequate number then this shouldn’t be a problem. However I feel there is still a possibility that the creatures aren’t going to do a good enough job due to low population or some other unknown factors. I guess I could go poking around in the substrate to find out if there are some problems with clumping and take measures in needs be.

Of course I’m open to suggestions on how to prolong the life of the substrate and being told that my ideas so far are completely off base!

 

[Scooterman]

It you dump more food then it will have to repopulate to accommodate, & thus will turn over you bed quicker but at a price, more creatures leads to more processed waste & eventually they will reach Maximum for your bed size then some will die off leading to more waste, these critters poops also at some level, which more smaller critters eats but same for them also, eventually whatever gets processed by all the critters will clump up, it doesn't vanish & if you take an aluminum can and smash it and smash more until it is very small, is the total mass any less? How can all the food just disappear, where does it go?

 

[NaH2O]

Originally posted by Scooterman
How can all the food just disappear, where does it go?

A good magician never reveals his secrets...

 

[Cougra]

Originally posted by NaH2O
With less critters, would the sand bed be fully functioning? I guess there would be enough life to keep things moving in it *(thinking out loud)*. Scott, I'm following what you are saying, I'm just trying to get a handle on this so I get the most out of my system by understanding it.

When I say remove sand I mean I’m going to change out a smaller portion of the bed, maybe and 1/8 of the substrate at a time. Yes this is going to hinder part of the sandbed until it can get repopulated, yes this is going to reduce the critter population however it’s also going to make room for the remaining critters to multiply in, this added with a new influx of bio-diversity from new live rock, trading sand from another tank or purchasing more critters, will help keep the critter population healthy.

 

[Scooterman]

 

[mojoreef]

OK...so let me see if I have this right....there is no way of preventing the phosphates from getting into the sand bed, because it is already present in the sand, and essentially it will leach....because if it's in the sand then it is going to be in the lower zone.

You cant control the phosphates that are in the sand, unless you dont put it in. You can control an ammount of the phosphates entering the bed by not allowing the phosphates that are associated with detritus/food/waste and so on to enter it but kinda defeats the purpose. The concept now being purposed by the PHd's is to allow the cyano/algae portion of the phosphate cycle to occur and then to syphon the cyano and so on out, this way you are breaking the cycle and actually exporting something.

However, I can control the top portion by syphoning the upper layers, say during water changes

you could but you have to becareful. two things to look out for. One is watch for the sulfide zone (grey sand) hit that and you could have problems. The second is you have to look at the whole bed. You are going to have the ananerobic zone raiseing in the bed (along with all the products that a DSB doesnt process), now at the same time you are shaving off the top....at some point in time your going to meet, hehehe

and having good water movement trying to keep the detritus in the water column

yep thats what folks do that dont have DSB's, this way it keeps the detritus as a food source for those that feed on it, or it lands in the bed and feeds it instead.

What about trying to keep the critters in the sand bed fed in order for their job to be done. If I keep removing their food source, then I potentially won't have critters.

The larger critters in a dsb (pods/worms and such) are thier for what is called bioturbation. Thier movement allows for the migration of elements through the bed. They are not really thier for thier reduction capabilities. They will find food dont worry, lol

What changes can I do to the system to make it work

Boy thats a question that even the big boys cant answer. Hun the DSB is what it is. A DSB is set up to be a recycling center not an export devicd (with the possible exception of nitrogen) .

Macro algaes in the fuge to absorb the phosphates

You can do that for sure, it will allow for the absorbtion of nutrients (both P and N) that are in the water cloumn and happen to come with in grasp of them. As per this helping a DSB, no chance. the phosphates bound with in the dsb system that are leached will be taken up on the spot by algae and will not be available to the marco that is somewhere else. This is why cyano is so previlant with dsb's, Cyano is a super absorber when compared to macros.

Mike

 

[NaH2O]

Thanks, Hun...I mean Mike ....I guess when I asked what can I do to make it work I meant what can I do to help it work.

One is watch for the sulfide zone (grey sand) hit that and you could have problems. The second is you have to look at the whole bed. You are going to have the ananerobic zone raiseing in the bed (along with all the products that a DSB doesnt process), now at the same time you are shaving off the top....at some point in time your going to meet, hehehe

I see what you are saying about the zones meeting eventually. What about introducing some live sand every so often...little by little in order to keep the zones separated?

When I say remove sand I mean I’m going to change out a smaller portion of the bed, maybe and 1/8 of the substrate at a time.

Michelle, I had planned on this as well. I wonder though if there is a build up of hydrogen sulfide (is that right?) when the sand is removed in the display...however much....would we run the risk of exposing our inhabitants? I also plan on having DSB in my fuge, which I will be able to take off-line and change out the substrate as maintenance.

Another point I guess should be made, is what depth of sand is considered DSB? I've planned a sand bed in my main system of ~4 inches at the highest point.

O.K. Mike, teach away......

 

[mojoreef]

Sorry about the hun thing, lol ..bad habit.
See Nikki this was the whole reason I started the plenum thread. The concept was to let everyone know how things work biologically, that way it gives you a better chance on manipulating it or know if what ever system can even work. Ok lets get to biz of breaking down a DSB.LOL
When looking at a system like this we have to look at limiting factors. knowing these can help us fool around.
When worrying about a bed going anaerobic, we can look at these limiting factors. the presence of oxygenated water will not allow it to go anaerobic, so we know then that we have to do that. Now because the grain size is so fine its harder (you can kinda see where I was going with particle size in the plenum) but not impossible. large stiring critters like cukes, or big stars stuff like that. Or a million worms and a billion pods. you could introduce more sand no problem, but I dont think it would make a big enough impact and as time goes by you wold have a sand tank, lol.
Even knowing the problems with a DSB I did one for 2 1/2 years, figuring I could out smart it and manipulate it to where I could make it work. Manualy stirring the bed and syphoning out the detritus that came out of it worked for me in keeping that upper level aerobic. With the rocks on top of part of the sand I couldnt do anything their but hope the bugs could manipulate. I spent hundreds of dollars of detrovoir kits and so on. The sand under the rock was anaerobic and had a sulphide zone 1/4 inch down. In the display I was able to keep the anaerobic zone down about an inch. Sulphide zone down about 1 1/2inches. I battled the phosphates (and believe me I know a few tricks) but couldnt win, the battle became more and more of a loss (as in cyano/algae blooms) were coming back more often and quicker. Their is no way a DSB cn deal with phosphates, you only chance is to make sure you limit the ammount you put in.
Can I ask you a question, why is it that you want one??

MIke

 

[RogueCorps]

Hey Mike,

Do you have a link to the case studies you've read or could you send me those?

Thanks!

-Rogue

 

[Scooterman]

He said Pods! Like he knew what he was saying, oh yea he does he does!:columbo:

 

[RogueCorps]

Not saying who is wrong or right here... just a couple of Ron-posts to remember that there are other opinions on the fate of DSBs. There are success stories as well as crashes, likely due to the thousands of possible variables in each and every tank. Still reading... Hmm...

-R

Hi Tim,

If you set up a sand bed as normal (see the the "Sand bed questions" sticky thread at the top of the forum listings) and use a low metals salt, along with good nutrient export, I see no reason that a sand bed can't last indefinitely.

On the other hand if you have hermit crabs, and sand sifting stars and fish, it will may be somewhat functional for at least a few days. After that... nope.

So...

The functionality of a sand bed is dependent upon the animals in it. Hermit crabs, and sand sifting animals kill and eat those animals and simultaneously kill the functionality of the sand bed.

This is your call... I can't advise you.


__________________
Cheers, Ron

Hi,

What has changed is simply that some people find that they are incapable of maintaining a functional deep sand bed. Because they don't seem to be able to use the methodology correctly (generally by ignoring the rules of setting up the bed properly and keeping the bed well stocked, as well as over crowding the tank), when the bed fails to live up to their expectations, they blame the failure on the sand bed rather their own deficiencies.

With some luck perhaps they will find some way to maintain the animals they wish to keep by doing something else.


__________________
Cheers, Ron

 

[RogueCorps]

-

 

[NaH2O]

Mike, don't worry about the hun thing...I was just dishing it back at ya....I've been called a lot of things in my life, and hun is probably one of the nicer ones . It actually made me laugh, and is helping to keep this discussion on the lighter side for me.

As for why I want a sand bed....well, I would like to keep some inhabitants that like a sand bed, aesthetics, and denitrification. I hope to keep my plan of having a light bio-load, and I'm going to make every effort not to overfeed.
Honostly, when I first started researching.... DSBs were all the rage, and they made sense to me. Of course, after I purchased my southdown, I began reading of issues some were having, but I still want to go ahead with the sand bed...I want to be as educated as I can about my choice. I see both sides of the debate, and hope that my tank will last a number of years. If or when it crashes....I'll just have to upgrade to a larger tank (always room for an upgrade). I will, however, give you the honor of saying, "I told you so" in public.....I'll even march around town wearing a wooden sign that says "Mike was right about sand beds", but only cuz I like ya!

Other than Rob....are there any others that have a long lasting DSB?

 

[mojoreef]

Sure RC, some are linkable some arent. I will post the abstract from the unlinkable ones for you.
Aquacultural Engineering
Volume 27, Issue 3 , March 2003, Pages 159-176

Water quality and nutrient budget in closed shrimp (Penaeus monodon)
Dhirendra Prasad Thakurm4.cor*m4.cor*, mailto:dpthakur@hotmail.commailto:dpthakur@hotmail.com, a, b and C. Kwei Lina

Nutrient budget revealed that shrimp could assimilate only 23–31% nitrogen and 10–13% phosphorus of the total inputs. The major source of nutrient input was feed, shrimp feed accounted for 76–92% nitrogen and 70–91% phosphorus of the total inputs. The major sinks of nutrients were in the sediment, which accounted for 14–53% nitrogen and 39–67% phosphorus of the total inputs.

Water Research
Volume 36, Issue 4 , February 2002, Pages 1007-1017

Phosphorus Budget as a water quality management tool for Closed aquatic mesocosms

Awesome Article in how the St. Lawrence Mesocosm at the Montreal Biodome have dealt with nitrates and phosphate reductions. It seems that they have tried for the last ten years to try to remedy the amounts of phosphates and nitrates in their setup. After close controlled experiments and nutrient removal they have developed what they feel as the only reliable reduction process and that’s using Large mechanical filters and cleaning them regularly and sucking out the detritus with an underwater vacuum cleaner.

Advances in Environmental Research
Volume 6, Issue 2 , March 2002, Pages 135-142
Field measurements of SOD and sedimenthit2hit2 nutrient hit1hit1fluxe****3hit3 in a land-locked embayment in Hong Kong
K. W. Chaum4.cor*m4.cor*, mailto:cekwchau@inet.polyu.edu.hkmailto:cekwchau@inet.polyu.edu.hk

Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong

It is logical that sediments in eutrophic water may contain enormous amounts of phosphorus existing in both organic and inorganic forms. Under aerobic conditions, a thin aerobic layer with a thickness of a few millimetres covering the sediments exists, which has been determined to be one of the factors contributing to the assimilation capacity of phosphorus. (Promeroy et al., 1965) When the condition changes to anaerobic, the ferric compounds are reduced and the sorption capacity substantially decreases. A free exchange of dissolved substances between the sediments and the overlying water takes place. Under such conditions, phosphorus will be gradually released into the overlying water.
Compared with phosphorus, the process of nitrogen release from sediments is more complicated since it involves the inter-conversion of a larger number of nitrogen species. It was noticed that ammonia nitrogen was, among others, the key form of nitrogen released from the sediment, which agreed well with results reported by Boynton et al. (1980). The release of a high concentration of ammonia nitrogen from the sediment is the result of the decomposition of organic nitrogen, which previously accumulated continuously in the sediment. The concentration of nitrate-nitrite nitrogen was found to be low since it can be released from or absorbed into the sediment, depending on the concentration gradient across the interface between sediment and water. When the external nutrient loadings or sources were gradually decreased and removed from Tolo Harbour, sediment previously enriched with nitrogen could still release sufficient nitrogen quantities to support the growth of plankton and hence improvement of water quality could not be achieved immediately.
It is also noted that the sediment release rate measurements are of the same order as those computed independently from a diagenesis model (Lee and Feleke, 1999).

Water Science & Technology Vol 42 No 3-4 pp 265–272 © IWA Publishing 2000

Non-steady variations of SOD and phosphate release rate due to changes in the quality of the overlying water
T Inoue*, Y Nakamura** and Y Adachi***
* Department of Maritime Systems Engineering, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
** Port and Harbour Research Institute, Ministry of Transport, 3-1-1 Nagase, Yokosuka, 239-0826, Japan
*** Department of Maritime Systems Engineering, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
--------------------
ABSTRACT
A dynamic model, which predicts non-steady variations in the sediment oxygen demand (SOD) and phosphate release rate, has been designed. This theoretical model consists of three diffusion equations with biochemical reactions for dissolved oxygen (DO), phosphate and ferrous iron. According to this model, step changes in the DO concentration and flow velocity produce drastic changes in the SOD and phosphate release rate within 10 minutes. The vigorous response of the SOD and phosphate release rate is caused by the difference in the time scale of diffusion in the water boundary layer and that of the biochemical reactions in the sediment. Secondly, a negative phosphate transfer from water to sediment can even occur under aerobic conditions. This is caused by the decrease in phosphate concentration in the aerobic layer due to adsorption.

http://www.terrapub.co.jp/journals/JO/pdf/5503/55030463.pdf

http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch10/group5.html

http://www.bact.wisc.edu/microtextbook/Metabolism/OtherAssim.html

Jaubert J., Marchioretti M., Priouzeau F., 1995. Carbon and calcium budgets in a semi-closed coral mesocosm. In: Proceedings of the 7th International Coral Reef Symposium, 289-293 (Boston, USA: April 1993).

Jaubert J., 1989. An integrated nitrifying-denitrifying biological system capable of purifying seawater in a closed circuit aquarium. Bull. Inst. Océanogr. Monaco. 5: 101-106

Boudreau B.P., Jørgensen, B.B., 2000. The Benthic Boundary Layer: Transport Processes and Biogeochemistry. Oxford University Press © 2000

 

[Curtswearing]

Curt typing slowly and quietly because a client is on the phone. Everything in this hobby has it's advantages and disadvantages. As long as people understand the issues, then you're golden.

 

[NaH2O]

Wow, Mike...it will take me some time to go through your post. I am, however, rather partial to the link from Purdue...as I'm an alumni.

 

[Curtswearing]

I was typing too slow. My clients attorney is paid by the hour and likes to hear his own voice too much.

 

[Scooterman]

 

[mojoreef]

Aller, R.C. 2000. The Benthic Boundary Layer: Transport Processes and Biogeochemistry, Ed. Bernard P. Boudreau, Bo Barker Jørgensen, Ch. 11. Transport and Reaction in the Bioirrigated Zone, Oxford University Press © 2000
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Marine Pollution Bulletin
Volume 20, Issue 12 , December 1989, Pages 624-628
Alteration of phosphorus dynamics during experimental eutrophication of enclosed marine ecosystems*1
Kenneth R. Hinga
Marine Ecosystems Research Laboratory, Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA
Available online 7 April 2003.
Abstract
A 28 month eutrophication experiment was conducted in marine mesocosms at the Marine Ecosystems Research Laboratory of the University of Rhode Island. Each mesocosm contained 13 m3 of seawater and a layer of benthic sediments transferred from adjacent Narragansett Bay. Nitrogen, phosphorus, and silica were added daily to the mesocosms.

The paper examines net exchanges of phosphorus between benthic sediments and water column during the experiment. At low loading rates the regular annual pattern of phosphate concentrations is still evident but the amplitude of the pattern is magnified. At higher loading rates the annual pattern is lost and the effectiveness of the sediments to act as a `buffer' to water column concentrations is reduced. In some cases the nutrient loading caused a release of phosphorus from the sediments.
--------------------------------------------------

Author/Editor/Inventor
Hopkinson Charles S, Jr [a]; Giblin Anney E; Tucker Jane; Garritt Robert H.
Institution
[a] Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA, 02543 USA.
Title (English)
Benthic metabolism and nutrient cycling along an estuarine salinity gradient.
Source
Estuaries. 22(4). Dec., 1999. 863-881.
Abstract
Benthic metabolism and nutrient exchange across the sediment-water interface were examined over an annual cycle at four sites along a freshwater to marine transect in the Parker River-Plum Island Sound estuary in northeastern Massachusetts, U.S. Sediment organic carbon content was highest at the freshwater site (10.3%) and decreased along the salinity gradient to 0.2% in the sandy sediments at the marine end of the estuary. C:N ratios were highest in the mid estuary (23:1) and lowest near the sea (11:1). Chlorophyll a in the surface sediments was high along the entire length of the estuary (39-57 mg chlorophyll a m-2) but especially so in the sandy marine sediments (172 mg chlorophyll a m-2). Chlorophyll a to phaeophytin ratios suggested most chlorophyll is detrital, except at the sandy marine site. Porewater sulfide values varied seasonally and between sites, reflecting both changes in sulfate availability as overlying water salinity changed and sediment metabolism. Patterns of sediment redox potential followed those of sulfide. Porewater profiles of inorganic N and P reflected strong seasonal patterns in remineralization, accumulation, and release. Highest porewater NH4+ values were found in upper and mid estuarine sediments, occasionally exceeding 1 mM N. Porewater nitrate was frequently absent, except in the sandy marine sediments where concentrations of 8 muM were often observed. Annual average respiration was lowest at the marine site (13 mmol O2 m-2 d-1 and 21 mmol TCO2 m-2 d-1) and highest in the mid estuary (130 mmol O2 m-2 d-1 and 170 mmol TCO2 m-2 d-1) where clam densities were also high. N2O and CH4 fluxes were low at all stations throughout the year. Over the course of a year, sediments varied from being sources to sinks of dissolved organic C and N, with the overall spatial pattern related closely to sediment organic content. There was little correlation between PO43- flux and metabolism, which we attribute to geochemical processes. At the two sites having the lowest salinities, PO43- flux was directed into the sediments. On average, between 22% and 32% of total system metabolism was attributable to the benthos. The mid estuary site was an exception as benthic metabolism accounted for 95% of the total, which is attributable to high densities of filter-feeding clams. Benthic remineralization supplied from less than 1% to over 190% of the N requirements and 0% to 21% of the P requirements of primary producers in this system. Estimates of denitrification calculated from stoichiometry of C and N fluxes ranged from 0% for the upper and mid estuary site to 35% for the freshwater site to 100% of sediment organic N remineralization at the marine site. We hypothesize that low values in the upper and mid estuary are attributable to enhanced NH4+ fluxes during summer due to desorption of exchangeable ammonium from rising porewater salinity. NH4+ desorption during summer may be a mechanism that maintains high rates of pelagic primary production at a time of low inorganic N inputs from the watershed.
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http://www.ukmarinesac.org.uk/communities/intersand-mud/ism5_5.htm

http://www.aoml.noaa.gov/ocd/sferpm/szmant/Brand_Szmant_Final.html
http://www.aoml.noaa.gov/ocd/sferpm/szmant/carlson/carlson.html

http://www.botany.hawaii.edu/Bot482/Kaneohe Bay algae N-P Larned Mar Biol.pdf

http://www.mpi-bremen.de/flux/


mike