Fall 2007 Sea Scope Article... DSB de/nitrification, olde hat    12/31/07
Hi. I've just read an interesting article by Bob Goemans discussing the effect of low and no oxygen areas in deep sand beds and other areas in the aquarium. It suggested that an 'ammonification' process is taking place in the lower levels (anoxic areas) of the sand bed and that the ammonium produced is then reprocessed back into Nitrite, Nitrate and along with Ammonium in the upper reaches of the DSB and leached back into the water.
The article raises serious questions about whether or not DSB's and live rock actually reduce nitrates.
<This is an ancient speculation... Can occur>
Having just set up a 72 bow front with almost 5 inches of aragonite in both the tank and the refugium and planning to buy 100 pounds or so of live rock, I would really like your opinion of the authors' contention in this article.
(It distresses me to see such basic issues as nitrate removal are still so unsettled. I rejoined this hobby after many years because I felt the technology and understanding of marine ecosystems had reached the point where such problems have been solved. I mean what's next, protein skimmers are actually found to increase DOC's?!!) Thanks for your views.
<I would not be overly concerned re this possibility... with some modicum of care in the selection, use of foods, their amounts, some circulation, decent mechanical et al filtration, regular maintenance (some stirring or vacuuming of part of the bed...) a disastrous cessation or reversal of nitrification is highly unlikely to occur. Search the name Tim Hovanec re some science re this/these issue/s in recent times. Bob Fenner>

Hydrogen sulfide  4/21/07
I am sorry to bother you guys again.  I have been reading thru your FAQ's but am still quite (even more so now) confused about substrates.  I do not want a DSB.  I have some special grade reef sand that I recently added to my tank after my live rock cured, about 3" deep.  
<Mmm, I'd increase this depth... about another inch>
I have my live rock on a PVC frame and needed this much to cover it up.  
Is this too deep?  
<Mmm, no... but is in-between "good levels">
I recently noticed some dark spots underneath my tank and definitely smell HS gas.  Would increasing the flow around those areas help with it?  
<Maybe... not necessarily H2S...>
My tank was doing fine until I added the substrate it seems.  My ammonia, nitrite and nitrate levels were all at 0 for over a week, so I added the substrate.  Today I checked the levels and ammonia was at 0.20, nitrite and nitrate 0.  I am doing twice weekly 30% water changes until the tank stabilizes again.  I just don't know what is causing the spike, I am worried it has something to do with my substrate.  I have 6 hermit crabs and 8 snails, which were added after the rock cured.
Also, is it normal for brown algae to grow on the live rock like it is now?  
<Yes...>
I hear stories about how people have cool stuff growing on there live rock, I haven't seen anything on mine yet and it's almost been a month.
Shanna
<Please read here: http://wetwebmedia.com/marine/setup/index.htm
scroll down to the brown line... on DSBs... Bob Fenner>

Sand and Nitrite, DSB Woes 4/17/07  James' go Hey guys. <Hi, whomever you are.> I have a problem here right now. Nitrite level is at 0.25ppm and my fishes died one at a time. It's really that horrible. Are fishes really that sensitive to nitrite level? <Is this a typo and meant nitrate?> I know that this is normally caused by increased in bioload. Let me update on some of my recent activities in the tank. Add in some snails recently and 4 of them died causing a foul smell in my tank. <This did not help matters any.> Then I introduced 4 new fishes into my tank. I have a DSB of 7inches in my refugium and it is supposed to be able to support my tank (no sand) of 50gallons. <Do not follow...DSB of 7 inches, (no sand)> I did a change of biological filter medium recently before addition of fishes. I took out the old ones and replace with better ones. But I didn't replace all of them at once. <Mmm, any live rock in the system?> I leave <left> out some old ones behind so that the bacteria are still around. I thought that the DSB will be able to support the tank but to my surprise, my nitrite level went up to 0.25ppm. I think the bioload possibly increased due to the demise of my snails and fishes. <Definitely helped the problem along.> And sadly, I am left with only a few fishes. The corals are intact. My clams and shrimps are all good and alive. No sign of Ich showed on my Powder Blue when it died. But some dark spots can be seen. <Tank would have been too small for this guy even if it were small, as they do require plenty of swimming room.> I still have a Powder Brown in my refugium but have placed it in a separate container of newly-prepared water. <Container sounds small, the fish probably won't last too long in that environment.> There are some color changes in my DSB. Some sand changes from yellow sand into grey color. I have included a picture on that. Is it caused by anaerobic bacteria? <Yes, can be caused by such.> When I try digging into the grey area, a lot of air bubbles coming out of the sand. <Nitrogen gas or hydrogen sulphide gas.  Does the sand/gravel have a rotten egg smell to it?  Pick a small handful up and give a whiff.> Despite having years of experience in reefing, this is the first time I see a change in coloration of my substrate. What caused that exactly? I do dose in medication for my fishes. <Not good, you are adding to your problems.  In my opinion, medications should only be used in quarantine tanks.  No effective pathogen/bacterial medication is completely safe irregardless of what it says on the bottle.> What I concluded and think is that the change of filter medium caused a breakdown in biological filtration with the addition of fishes and the demise of one after another, the biological system cannot support and thus increasing in nitrite level. But what I am more worried and suspicious of is that of my DSB, I fear that the bacteria are dying and that contributes to the reason why the DSB can't support my tank anymore. It spells trouble for me. <First, stop medicating and do read here and related links, so you have an understanding of how these systems work when set up properly.  http://www.wetwebmedia.com/deepsandbeds.htm> I will <would> like to hear you out on that and some of ur <your> opinion. I'm not adding anymore stuffs in until I have find a solution or answer for that. <I wouldn't add any more stuffs either, but also would not add any more fish or invertebrates.> I am afraid the medication and ozone are causing the lose of bacteria. <You do not sound like you have years of reef experience.  Some of the problems you have mentioned should not have happened to an experienced aquarist.  Please read above, my friend.  I could not open the picture files, maybe Mr. Fenner can. <James (Salty Dog)>

Sand and Nitrite 4/17/07  Chris' go Hey guys. <Hello> I have a problem here right now. Nitrite level is at 0.25ppm and my fishes died one at a time. It's really that horrible. Are fishes really that sensitive to nitrite level?  <Yes, is quite toxic, nitrate is much less toxic, and the next step in the nitrogen cycle.> I know that this is normally caused by increase in bioload.  <Or overfeeding, or a crash of the bacterial population brought on by many different factors.> Let me update on some of my recent activities in the tank. Add in some snails recently and 4 of them died causing a foul smell in my tank. <Decaying organic matter, probably the source of the nitrite.> Then I introduce 4 new fishes into my tank. I have a DSB of 7inches in my refugium and it is supposed to be able to support my tank (no sand) of 50gallons.  <Do you have LR, generally a sandbed alone will not have sufficient surface area to do all the biological filtration.> I did a change of biological filter medium recently before addition of fishes.  <Probably added to the decrease in biological filtration capacity.> I took out the old ones and replace with better ones. But I didn't replace all of them at once.  <Need to space this out over weeks most likely.> I leave out some old ones behind so that the bacteria are still around.  <But it needs time to recolonize the new media.> I thought that the DSB will be able to support the tank but to my surprise, my nitrite level went up to 0.25ppm. I think the bioload possibly increased due to the demise of my snails and fishes. <I think you have unrealistic expectations of what a DSB is capable of.  Only the top inch or so of the DSB will help in Ammonia - Nitrite conversion.  Any deeper and there is not enough oxygen to accomplish this.  This is where the DSB can convert nitrate to nitrogen gas and keep nitrate lower.  Are you confusing nitrite and nitrate maybe?> And sadly, I am left with only a few fishes. The corals are intact. My clams and shrimps are all good and alive. No sign of Ich is showed on my powder blue when it died. But some dark spots can be seen.  <May just be stress or death markings, hard to say.> I still have a powder brown in my refugium but have placed it in a separate container of newly-prepared water.  <Filtered hopefully.> There are some color changes in my DSB. Some sand changes from yellow sand into grey color. I have included a picture on that. Is it caused by anaerobic bacteria ? When I try digging into the grey area, a lot of air bubbles coming out of the sand. <Could be areas of hydrogen sulfide, but you would smell it, smells like rotten eggs.  Hopefully just Nitrogen gas and the color changes just the waxing and waning of algae living along the glass.> Despite having years of experience in reefing, this is the first time I see a change in coloration of my substrate. What caused that exactly ? I do dose in medication for my fishes.  <What medications?  Why?  What are you trying to treat?> What I concluded and think is that the change of filter medium caused a breakdown in biological filtration with the addition of fishes and the demise of one after another, the biological system cannot support and thus increasing in nitrite level. But what I am more worried and suspicious of is that of my DSB, I fear that the bacteria are dying and that contributes to the reason why the DSB can't support my tank anymore. It spells trouble for me.  <The DSB works just like a shallow bed as far as nitrite reduction is concerned.  DSB used mainly for nitrate reduction.> I will like to hear you out on that and some of your opinion. I'm not adding anymore stuffs in until I have find a solution or answer for that.  <Good.> I am afraid if the medication and ozone are causing the lose of bacteria.  <Adding medication to the main tank is never a good idea.> <Chris>

No More DSB?
This question is for Jim. Yesterday (09/13/04), in one of your responses you stated that you are finished with DSB's and are going to stick with a shallow sand bed.  Could you share your reasons for doing so because I really have only read beneficial rationale for keeping a DSB.  It would be nice to be able to consider some of the downsides of a DSB.
>>>Hi Corey,
Some reefers are steering away from DSB's, and I may be joining their ranks. While it was once thought that certain functions take place only in the deeper parts of a sand bed, it SEEMS as though this isn't really the case. Apparently, a shallow sand bed is just as effective. I say "apparently" because this seems to be what recent empirical data indicates. Sooner or later it seems, most sand beds crash. Dr. Ron Shimek says no, not if properly maintained. The bottom line is, the jury is still out on this issue. Other reasons, they take up space in the tank, and when the day comes that you have to move the tank for any reason, moving a sand bed is a HUGE job all by itself. This I know. :)
Really, I'm just over it, and I see many successful tanks without them. When will I start pulling mine? Who knows. :) I'll never go bare bottom, I hate that, and I still need a bit of sand, maybe 2" to sit my clams in.
Jim<<<

The Old "DSB Crashing" Query
Dear WWM crew, <Hello! Ryan with you today>
  I really apologize for asking too many questions, but I have no one else to ask...<That's kind of sad!  Happy to help> I have a 3" to 4.5" sandbed that consists of a 1" layer of carbonate sand that is so fine it is almost like baking soda. <Great> On top of that is a 1.5" layer of aragonite that is between .05mm to .2 mm, and finally a .5" to 2" layer of .2mm to .5mm aragonite. The bottom two layers are over a year old and the top layer is a bit over 2 months old. <OK>
  During a pre-vacation 2 X 25% water change, I decided to vacuum the top half inch layer of sand for the first time ever. Most of the sand yielded a yellowish muck that made the drained water look like a 10% Kent Marine Microvert solution in water -proof that my DSB is accumulating nutrients at the very least -my nitrates tested zero yesterday. <I'm sure you stirred up quite a scene>
Sand from the rear corners of the aquarium however was pitch black just below the surface and I decided to vacuum off the whole lot on one side but left the other side alone, only slightly disturbed. The sand here smelt like hydrogen sulfide!!! I guess I need more circulation in the corners. <Yes, and perhaps a better skimmer> At this
point, can I save my DSB by removing all the black sand and replacing it with new sand and adding more power heads pointing to the corners? Or should I leave it alone and just add the powerheads in the middle pointing to the corners? Currently I have three power heads in various corners pointing towards the center. <I'd use a powerhead that is designed to move lots of water, with a soft touch.  Check out Tunze Streams, or Rio Seios.>
As for routine maintenance in the future, I intend to vacuum the top .5" regularly, removing it and replacing it every six months. Any comments on this one?
<Increase overall sand depth to 6+ inches of powder fine sand, never touch it again.  The most sandbed duty you should need to do is to add a fresh handful from time to time to keep your bacteria populations in check!>
I can't thank you guys enough!!!
<No problem! Good luck, Ryan>
Narayan

Playing With Sand (Deep Sand Beds)
Hi crew!
<Hello there! Scott F. with you today!>
Firstly, thanks to Matt for answering my last queries!
<Attaboy, Matt!>
Just been speaking to my LFS and wanted a second opinion on a couple of things. I've got a plenum in my sump with 4" of aragonite, and about 3" of aragonite in the open/visible parts of my display (live sand added over dead rock when tank first set up so it will have sneaked into gaps creating an uneven bed). I'm wanting to up the DSB to >3" and also get some in the "caves/hollows" so that the whole base is this deep.
I was told that it was detrimental to have a DSB when I've got the plenum in the sump and I would be better taking the DSB out completely i.e. <1/2".
<I'm not sure why this would be considered detrimental. Properly maintained plenums or "static" DSBs are beneficial. Perhaps it's redundant to have two sand beds, but I am not sure what the disadvantage could be, short of taking up lots of space...>
It cost me a fair bit of money (over 100lbs of sand) so don't want to do this in a hurry, but then don't want to buy more sand if it is detrimental. The argument was the risk of ph crash with the DSB due to detritus build-up - i.e.. living on a knife edge where something could tip it over to a point where I couldn't react fast enough to fixing it.
<I think that is a speculative argument based on largely anecdotal evidence. In fact, thousands of hobbyists, myself included, have maintained DSBs for years without any problems whatsoever. I think that the "DSB becomes a nutrient sink that will crash your tank" argument is based upon several people having bad experiences and then going wild on the popular reefkeeping message boards touting the detriments of DSBs. A properly developed, well maintained DSB in a tank with overall good husbandry techniques is an excellent way to successfully maintain a reef system. The key is attention to proper husbandry. DSB's are not a miracle, but they are not recipes for disaster, either. Attention to water quality, feeding, etc., vital in any system, are also critical in a DSB-based system.>
I was also told that I shouldn't use aragonite in the sump as it will gradually (within a year) bond into a solid lump.
<Well, this is true if you do not stir it up a bit once in a while. This can occur in the display tank as well as the sump, BTW.>
I've got a spare 20lb bag of LS to add, but I've been told that it is dangerous to add LS to a stocked system as it would swallow up the oxygen.
<Well, I'd add it gradually. Any change made to an existing system should be made slowly, and adding more live sand is no exception to this rule >
It all threw me somewhat!
<I can imagine!>
Bought some Kalkwasser whilst there for my top up but wasn't sure how (or when) to use it. My calcium is about 350? Should I be adding it? On the pot it says to mix up separately and drip siphon in. I can't work out how this applies to my top up tank. Do I just pop the required amount straight into my top up (it's heated and aerated) as it is added very gradually to the tank (i.e. a week+) by the level controller?
<Well, there are a number of different ways to add Kalkwasser, ranging from exotic drip systems to simply dumping in the Kalkwasser in a "slurry"; the amount you need to add is based upon testing. Do read up about Kalkwasser additions right here on the WWM site, or in Anthony Calfo's invaluable "Book of Coral Propagation", which discusses the simple "slurry" technique in greater detail.>
Thanks again in advance.
Peter
<My pleasure, Peter. I'm glad that you are skeptical of some of the advice that you hear. If you have a doubt about any advice you receive (including ours!), it's always a good idea to get a second (or third) opinion if you have doubts. Good luck! Regards, Scott F.>

Deep Sand Bed (Max Depth?) - 05/16/05
One article reads: 
"The depth of the bed (and particle size) are critical to provide the correct conditions. If the sand bed is not deep enough, and the oxygen level does not drop enough, the sand bed will produce nitrite from the nitrate. A disaster. Conversely, if the sand bed is too deep, the entire bottom of the bed can turn anoxic and produce sulfur dioxide. If this happens the affected sand turns black. If this black area is disturbed or sampled it releases the characteristic rotten egg smell. This chemical is of course toxic" 
What is too deep? what is the max a DSB can be?
<Is this from the WWM Website? <<Is assuredly not. RMF>> Do have a read here and at the related links in blue at the top of the page - http://www.wetwebmedia.com/deepsandbeds.htm  Regards, Eric R.>

- DSB, Sand Selection, and DIY LR Questions -
Hello, WWM Member!
It's so nice to have such a great resource to help those of us without a lot of hobby experience.  I'm still in the planning stages for a 70-90g peaceful reef tank, and I'm confused on certain points.  I have done TONS of reading on WWM regarding these questions, and I haven't found consistent answers... perhaps some of my questions have no conclusive answers!
First, regarding DSBs.  I know that optimally, 6"+ is best.  Is 6" optimal? <Six inches is the minimum, not optimal. Eight to ten inches would probably be optimal, if not always practical.> If not, what's the optimal depth?  (I know that making it too deep can cause hydrogen sulfide problems; at what depth do problems develop?) <Not sure this is empirical. I have a 12" DSB sump that's been running for a year and have had no problems with hydrogen sulphide. Think sulphide problem may result from sub-optimal depths, where the proper bacteria that would make use of this stuff do not exist.>
I've done a lot of reading regarding substrates, and I'm confused.  I've read that Jawfish and other burrowers are best kept in fine sand with some coarse material to aid their burrowing, and that these fish move around the bigger pieces to their liking; I've also read that coarser material mixed in won't harm anyone.  However, I've also frequently read that you shouldn't mix substrate sizes so channeling/packing is minimized. <I mix substrate sizes all the time - especially in the fish tank - seems to allow for better fauna development in the substrate.> So, the question: if I'm keeping Jawfishes, gobies, and the like, what should I do?  Should I stick with pure sugar-fine aragonite sand, or add some crushed coral, or add even coarser material like crushed shell? <I'd do all three.> If I should have coarse material, what ratio is best? <Perhaps 1/3 of each.> I just want to make sure they have the best substrate possible.
Also, I'd like to make some GARF Aragocrete "Reef Tables" and a couple caves for my tank (I'll have plenty of "real" live rock, of course).  I've heard some people have no problems, and others make claims that the cement adversely affects tank chemistry.  What's the truth? <The truth is that anything cementacious would need to be cured for a while - months - in a weak acid solution (vinegar would do) to help bring down the highly alkaline nature of cement products.> Would I be foolish to use Aragocrete, or will I be fine? <No... this has been done for decades in public aquariums and the like - is perfectly viable as long as you take the appropriate precautions.>
Oh, one last thing, if I may.  I plan on principally keeping quiet fishes, like gobies, Banggai Cardinals, blennies, and perhaps a Jawfish or eventually a mandarin (with a refugium, of course).  But... I (and my wife) would love to have a yellow tang (Zebrasoma flavescens).  Would it be too boisterous or aggressive a feeder to mix in this type of tank? <Would be fine.> I'm worried that the other fish wouldn't get enough food... Also, is there any species of clownfish that could coexist peacefully, as well, or are they too aggressive? <My favorite are the true and false percula clowns - they seems to be the most docile of all the clowns and seem to get along with just about anyone that won't eat them.>
Thanks so much for your time and help; I truly appreciate your advice.
Scott
<Cheers, J -- >

Anorexic Anaerobic Bacteria  8/27/05
Dear Crew:
<Paul>
Six months ago, I started a 75-gallon reef aquarium with an inline 29-gallon refuge sump.  My plan for natural nitrate reduction (NNR) was to reduce nitrates to nitrogen gas by cultivating anaerobic bacteria with a deep sand bed (DSB) and live rock.
<Okay>
During the first 5 months of this aquarium, I performed 25% water changes every week to keep the nitrate levels under control.  I want to be able to reduce my need for water changes with NNR but this does not appear to be happening. Last month, I decided to wait 4 weeks before changing the water.
While the ammonia and nitrite levels remained near zero, I found that my nitrate levels had climbed to between 25 and 50 ppm per the Salifert Nitrate Test.
<High>
I can add macroalgae to my refuge sump for nitrate export but I'd rather do that as a last resort.
<Why?>
Currently, my refugium is only used for water changes and houses an Iwaki MD30 pump, a Jager heater, an Ice Cap fan, and a Remora protein skimmer with carbon filtration.
I need your advice on what I must do to achieve NNR with a DSB and LR in the main tank.  The DSB is 4" deep on average and contains sugar-fine oolitic Pure Caribbean Aragonite from Petroglyph.   While it is full of bubbles when viewed from the side and contains feather dusters, I see no bubbles on the surface of the DSB.  Most of the main tank's volume is occupied by live rock covered with purple coralline algae and Pachyclavularia violacea but no observable bubbles.  The tank has a generous 10x water flow and 300 watts of DE-halide illumination with fluorescent supplements.
Everything else in the tank seems to be thriving:
1 Condylactis anemone (left end of tank)
1 Ritteri anemone (right end of tank)
2 Green Fiji Trees
Discosoma mushrooms
Rhodactis mushrooms
Pachyclavularia violacea
Palythoa
Assorted button polyps
Halimeda algae
1 Maroon Clown
1 Flame Hawkfish
10 Blue Devil Damsels
10 Pajama Cardinals
Asteroidea sand-sifting starfish
Turbo snails
Hermit crab cleanup crew
(1) What more must I do to cultivate the anaerobic bacteria needed to reduce nitrates to nitrogen gas?
<Perhaps add a couple more inches of substrate... I would>
(2) Are there nitrate-reducing anaerobic bacteria cultures that I can buy?
<Mmm, unnecessary>
(3) Has anyone succeeded in NNR with a DSB and LR in the main tank without macroalgae and frequent water changes?
<Yes>
My anaerobic bacteria are anorexic!
<Heeee! Do consider removing some/all of the LR from the refugium, adding macroalgae and a reverse daylight photoperiod there. Bob Fenner>
-Paul.

DSB and Tank Water Emergency  SOS
Hi Crew:  this SOS is directed to Anthony, and if he is not there, the deep sand bed specialists in the group.
<cheers, Connie>
My husband installed a new Rio 1100 powerhead at one end of our 60 gallon tank last night.  It fell off a couple of times as he can't seem to get those black round things to hold it.  It did a lot of damage to the sand bed at that end of the tank.  He then tied it up in some way  to the canopy to hold it there "temporarily".
<those suction cups for all such pumps are really weak. Its always best to use the clamps provided. If you must use the cups... then drop the water level in the tank temporarily and silicone the suctions in place.>
Meantime, he moved the powerhead at the other end of the tank and it fell off during the night and has blown the sand bed away to within 1" of the bottom of the tank.  Now he tied that one up too.
He tells me he has searched your website for these answers:
1.  The sand bed is a one-year old fully stocked 5-6" deep sand bed.  Has this opened up dead areas in the sand bed and are poisonous gasses leaking into the tank?
<nope... the poisonous gas fear is a boogey man. It rarely occurs and only exists in truly neglected tanks>
2.  We had just done a water change and are low on RO water with very little reserve.  What will happen to the water?  It has tested okay for nitrates, ammonia, etc.  so far   What has happened to my seeded sand bed?  Has this killed all the critters?  
<none of the above... little or no harm was done I assure you. Test to verify and do another water change in days/week(s) if needed>
3.  I have four small fish in the tank, should I removed them to my 30 gallon which has 3 small fish in it until everything dies down in the tank and I smooth out the sand bed?
<Yikes... not needed as per above>
4.  We can buy seawater at LFS and replace water if we have to.  I am also worried about all my live rock and the critters that dwell therein.  If I blow off the sand it will pollute the water, that is, can all these fish survive another sandstorm from cleaning off the rock?  The water has just started to clear now.
<do siphon or blow the sand off the rocks... and think of it exactly like a storm in the ocean. These creatures are largely used to it>
I am in the middle of a bad situation here and don't know what to do.
<have a beer. You'll feel better. At least, I know I'd feel better. OK... play some Moody Blues or Pink Floyd too to play it safe>
Also, isn't there SOME WAY we can glue these black rubber things onto acrylic tanks so that this doesn't happen.  My husband, the perpetrator, says he searched your website high and low for answers.
<no worries... do silicone them if the clamps are not an option. Its also really not tough to make a clamp with plastic stock sheet or even PVC pipe and some cable ties to fix the power head at any depth you might like>
Many thanks for your help on this one. Connie
<happy holidays, my friend... Anthony>

DSB, anoxic dilemma? 3/18/04 (Perhaps the term hypoxic for the mid-zone)
Hi bob,
<Anthony Calfo in his stead>
I have a question regarding depth of substrate. You mention to use 1" or less (completely aerobic) and 3" or more to create an anaerobic environment for denitrification. You mention any substrate thickness in between those parameters would cause anoxic havoc. I'm a little perplexed by this.
<me too... I am nearly certain Bob would have never said this... and I agree with part of the assertion, but would not use the phrase "anoxic havoc". Where is this from  my friend. Our book, the archives, etc?>
Firstly, the anoxic environment created by 2 inches is still an anoxic environment and I do not understand how it differs from 3 or more inches of substrate?
<part of the misunderstanding indeed... I do not believe a 2" substrate can get adequately anoxic for NNR... and if you'll take the time/years to use and study DSBs, the you will see that 3"/75 mm is the bare minimum for effective NNR... hence the rule>
Wouldn't both anoxic environments (in between 1-3 inches and 3" plus) create H2S?
<not the goal at either depth, and regardless cannot be assumed without an address of nutrients sunk to feed/fuel the conversion>
How is it that one is safer than the other? I'm sure there is something I am missing here,
<yes>
I just want to understand what that is.
<me too>
Please do not refrain from becoming really technical in order to get the point across (that is if you have time to), that is, layman's terms are not necessary, nor is the need to explain technical terms.
<no time alas at length... but please let me direct you to the extensive detail and discussion we have of it in our "Reef Invertebrates" book or the free wetwebmedia.com archives (much info there if you will take the time to sort through it)>
My last question. Why would one want to rid Live rock of its biodiversity...i.e.. removal of mantis shrimp...etc. How would they be detrimental to 1) fish only tanks or 2) reef tanks? Are these animals prone to being hosts of pathogens detrimental to animals/organisms in the tank more so than animals commonly kept in aquaria? Or do they just eat factors important in maintaining good water chemistry? Why are they deemed unwanted?
<depends on the species. You must ID that first. Spearers catch and kill fishes... even the smallest/"safest" smashers instead still mow through other desirable invertebrates like gastropods. Judge them by what you deem more useful in your aquarium... purchased snails/fishes... or expensive meals>
Thanks so much! Mars
<rock on... Anthony>

DSB, anoxic dilemma? II 3/19/04
...so my apologies. I replied to an e-mail regarding the quote below:
[I have a question regarding depth of substrate. You mention to use 1" or less (completely aerobic) and 3" or more to create an anaerobic environment for denitrification. ] You mention any substrate thickness in between those parameters would cause anoxic havoc. I'm a little perplexed by this.
<me too... I am nearly certain Bob would have never said this... and I agree with part of the assertion, but would not use the phrase "anoxic havoc". Where is this from  my friend. Our book, the archives, etc?>
Someone else said "anoxic havoc"
<<no worries... am following along>>
(Not your site...again my apologies). What was said in one of your archives was it was dangerous to have a sand bed
between 1"-3". Here is the quote:
[Sand Confusion: Aesthetics or Denitrification?
Anthony, I'm confused about the proper depth of substrate. Below is what you said in one of your letters. I don't get it. It seems contradictory. What's best, 1/2 inch, 3 inches, or 5???? Your words are in the red. Thanks! Pam PS]
I'm really not trying to be confrontational, I just want to understand!
<<Hmmm... you need to consider the sources my friend, and most importantly, the specific circumstances. We give advice based on each given scenario... and there is no one "magic" rule that works best for all systems. I'll recommend different substrates (grains/depths, etc) for fishless, versus small fish, versus heavy fish displays. They are very different bioloads. Furthermore... each aquarist has different benefits prioritized in what they would like to get from their sand beds. You simply cannot nail this down to a single rule my friend. You are also reading and quoting multiple authors here... Bob, me, Steve Pro (below) and other web sites. Not a fair comparison between different >
[I figured I would answer your question because I am here and we have pretty much the same point of view on this subject. If you have no sand, zero inches deep, a bare bottom tank, you are OK. As you add sand, you are OK until 1" deep. At this point all of the sand is aerobic (contains water with oxygen in it). As you go over one inch, you change from a completely aerobic environment but not to a true Deep Sand Bed (DSB). Deep is the imperative word. You do not get all of the benefits until you reach 3" or greater. In between 1 to 3 inches is a sort of no man's lands for denitrification. I hope this gives you a better understanding. -Steven Pro>>
The substrate is about 1/2 inch in the front and increases to about 2 inches in the back.
<dangerous in my opinion. Too thick to be aerobic but not thick enough to be helpfully anoxic. Just dangerous, and the reason why so many other reefers have inaccurately faulted "deep" sand beds. The rule stands at 1/2 inch or less, or more than three inches (I prefer a five inch minimum for denitrification. Anthony>
Why is it dangerous? How is it different in having a sand bed over 3"?  Thanks again!!! Mars
<<I don't think I can spell it out any more clearly than it has been in our archives and books. In practical applications - typical reef aquariums that are poorly planned mixed garden reefs (LPS, SPS, clams, etc... all together unnaturally at times) with modest to poor water flow... with modest to poor water change schedules... with weak skimming, etc... all of the common flaws in beginner to intermediate aquarists aquariums.... these are not conducive to succeeding with sand beds in the 1-3" range. Finesse husbandry and you can then finesse and employ most any depth of sand successfully (good water flow, sand stirring, aggressive skimming and water changes of 15-20%+ weekly, etc). regards, Anthony>>

DBS, anoxic dilemma? III 3/19/04
I think we all share the same view point. Thanks for your opinion and input. I think I'm clear on all this now (actually I'm sure of it). Just wanted to make sure i wasn't missing anything and you and your team have reinforced my beliefs.
<excellent... this is truly the benefit of getting a wide range of opinions... making a confident decision based on an intelligent consensus>
I must say you guys are speedy with the replies, so far I'd say you
guys are the best source of info I've come across. Keep up the good work and thanks a lot!!!
<it is a labor of love :)>
Cheers! mars
<best of luck to you, mate. Anthony>

Blame It On The Sand?
Hi all,
<Hey there! Scott F. with you today>
I have a question about my DSB. I had a Cyano outbreak in my tank and was chatting with a friend about it, and he was convinced I needed to remove my DSB. I am not one to have knee-jerk reactions based on one problem so I wanted to get your opinion on the matter. I have a 4" DSB with fine (sugar sized) aragonite I have the turnover on my pre-drilled Oceanic 75gal maxed out, any more turn over and I'm overflowing on to the carpet ;). All of the flow is created by the returns.
I use a manifold system with 3 outputs; no power heads. My friend is convinced that the problems originate form the DSB and the small sections of visible gray areas. Are these gray areas really bad?
<A lot of times, these are simply areas of coralline algae, or perhaps some aggregations of micro-organisms thriving in the layer between the front glass and the sand. Before blaming your DSB, do a thorough set of water tests, and see if there are other factors at work, such as phosphates in source water, etc. Lots of ways to address these, such as aggressive nutrient export mechanisms (protein skimming, etc.). There has been a lot of talk lately on the various internet discussion boards blaming DSBs for all sorts of problems. I'd be patient and stick with the DSB method, myself.>
There are some spots that you can see in the lower parts of the DSB thru the glass. I was wondering if this is a cause for alarm and therefore a misapplication of a DSB on my part or if I should look into other possible solutions like adding a power head (I was really trying to avoid this with my original design; using a manifold.) Please advise, and thanks in advance for all the help.
<I'd look at a variety of factors before blaming the DSB for this bloom. Sometimes, it's as simple as an RO membrane that needs replacement, or a protein skimmer that's not getting the job done. If your DSB has been constructed in accordance with generally accepted techniques, I'd have faith in the organisms residing there, and give it more time to do its job!>
The volunteers at WWM ROCK!
Ryan
<WWM readers ROCK! Regards, Scott F>

Don't Fear The Sand (Unfounded DSB Fears?)
Crew,
<Scott F. here tonight>
You guys are great... Thank you for the fast response and great advice.  I have a few more questions for you though...   Just a point of clarification, at your suggestion, I'm planning to order some amphipods and other bugs from IPSF.com.  Until I make the order, a stirring of the gravel bed (not to exceed 1 inch in depth) is an acceptable alternative to the bugs?  How much of the bed do I stir, and how often?
<Sure. I'd stir once every week or so, and just enough to keep the substrate from clumping>
Now on to another topic....  At WetWebMedia's FAQ's, and some other marine forums, I've heard many people knock the concept of the DSB as dangerous, not just because of the "nutrient sink" theory, which we discussed earlier, but also because of the possible production of Hydrogen Sulfide.  While I view most of this as nothing more than uninformed hysteria, (As I stated in my previous email I was confident enough to install a 6" DSB) I hear these hysterical ramblings so often that it does give me a moment of pause....  For my own piece of mind, Can you explain the processes behind the formation of Hydrogen Sulfide in Marine Aquaria, the likelihood of it occurring, and the best maintenance practices to avoid it?
Richard
<Well, Richard- that's a pretty tall order in the limited space that we have here...Whole books (Shimek, Goeman's, and others) have been devoted to the subject. In a nutshell, the formation of hydrogen sulfide is largely overstated, IMO. Yes, hydrogen sulfide will form in the lower parts of a deep sand bed. However, it will not emerge from the sandbed to poison the tank. It will flow up with water to shallower sections of the sandbed, where it is converted into sulphate, which animals utilize. Essentially, there will be no release of this stuff into the water column. Yes- it's more complicated than that, but you get the idea. Hope this helps alleviate some of your fears. Good luck! Regards, Scott F>

Macroalgae and DSBs 11/2/03 
Hi, I am looking to add macro algae to a new sump. Can you tell me the best kind to use? 
<that depends on many factors... but Chaetomorpha (Spaghetti algae) is hands down one of the best overall. Gracilaria is also quite good. Avoid Caulerpa in my opinion. See about all and why in the FAQs and archives of our site at wetwebmedia.com> 
I thought about mixing a few kinds together, but I read one response in a reef forum, and it said that you can make a mistake adding different types of algae together (maybe Gracilaria and Chaetomorpha?... 
<all algae fight (allelopathy) and one will ultimately succeed all at the expense of considerable energies. Pick only one species per tank> 
I don't remember for sure). They actually compete against each other and can become toxic. 
<yes... to each other, to invertebrates... and even to some fishes> 
I didn't know mixing macro algae could do that. That's not what I had in mind to do :-) This response also said the grape Caulerpa being one of the most noxious of all of the algae. Is that true? 
<very true by a remarkable scale of magnitude> 
I thought it was a good kind to have? 
<Caulerpa can be a boon or scourge. I dissuade folks from it because it is too labor intensive for most folks> 
The response also talked about macro algae going 'asexual' and becoming toxic. What does this mean? I have never heard of this either. 
<please do a keyword search of this topic and any other that interests you with the google search tool from our home page at www.wetwebmedia.com and all will be revealed to you my friend> 
Secondly, I read in another forum where a lot of reefers were talking about having reef tanks with bare bottoms (either no sandbed at all or a very small sandbed. They ripped deep sand beds talking about DSB crashes and really messing up tanks. 
<removing DSBs is a knee-jerk reaction by aquarists that have improperly installed them or have poor tank husbandry overall (usually inadequate water flow). We explain this dynamic at great length (tens of pages) in our book "Reef Invertebrates"> 
I have never heard of this and have never thought of having a tank with no sand at all. Everything I have ever read talks about live sand being a very important part of biological filtration. 
<agreed... there are tremendous benefits to live sand and rock methods> 
I am confused. 
<just need to read/research more my friend... and not so much from message boards with much opinion and inexperience (or limited experience) but from tenured and objective sources/authors> 
Can you tell me your take on having deep, medium, shallow, or no sandbeds? 
<I wish to help here my fried... but a proper answer cannot be relayed in an e-mail less than 20 pages! Please do simply read through our archives or if you feel frisky, that new book of hours is months old and covers all of these topics at great length. The most comprehensive in the industry to date> 
Thanks, Paul 
<best regards, Anthony Calfo>?

DSB redux... redux... getting reduxulous 11/5/03 
Hi crew members. I am writing about DSB and if they are still any good. On two big bulletin boards there have been a rush of respected people who have gotten rid of them because they are phosphate trap or have "crashed". Have you guys read those threads? 
<we have responded to others in recent days with queries of this nature> 
Lately they have gotten very heated and people have all kinds of info hat is over my head to back it up. Now I am starting to worry. 
<you have nothing to worry about if you have adequate water flow (10-20X) over any depth of sand, and good nutrient export processes (skimmers, water changes, etc)> 
Do you think those people have a good point? 
<the critics are misguided by their own misinterpretation of the correct way to employ a good DSB in my opinion.> 
Also have there been many DSB that you know of that are over 5 or 8 years old? Is that rare to find? 
<not rare at all... the methodology is quite old (public aquaria - decades). I have written about this topic at length in my "Book of Coral Propagation" and more so in our latest "Reef Invertebrates" (almost 40 pages dedicated to live sand and refugiums). In the last decade I have purchased and used 48,000 lbs of fine aragonite sand for DSB strategies in aquaculture (just as other pioneers like Dick Perrin at Tropicorium have). I can assure you that DSBs are easy to operate once understood and maintained properly... and have many outstanding benefits. They are time-tested IMO> 
Thank you 
<best regards, Anthony> 

DSB opinion 11/5/03 
To Bob and Anthony reef central has had 50,900 people view deep sand beds and the problems with them could both of you give me your ideas on all of this? Thanks RGibson 
<cheers, Ralph... our position on the matter (pros and cons) is spelled out in a fantastic new book <;)> that I happen to know you have in your possession, "Reef Invertebrates" by Calfo and Fenner. It is truly the most comprehensive coverage on the topic to date (nearly 40 pages dedicated to live sand and refugiums). A review may require more time in the lav. Ha! kindly, Anthony> 

Deep Sand Bed 3/19/03
Hi Crew ...
<cheers!>
As always I would like to thank everyone at WWM for giving us hobbyists the support and knowledge we hobbyist are in great need of.
<thanks kindly... its our pleasure/biz and life>
To my questions. I have put down a Southdown Tropical Caribbean play sand DSB of about 4 inches or so, on the bottom of my tank. God was it a hassle to get the sand to settle. But finally it did. My problem is that I have a clown fish that loves to dig. And almost everyday the clown makes a mess making the water all cloudy and takes almost a whole day to settle down again, the sand that is.
<bummer>
I have a FO tank and I'm thinking of getting some LR, about 30lbs or so. What do I do to keep that clown from making such a mess?
<it will likely be hard to dissuade the behavior. You may try to find a surrogate host/nest. A large empty decorative shell (like a conch) often works... else remove the frisky bugger>
Another question if I may. My tank chemistry is out of whack after introducing the sand.
<unusual... but will settle in less than 2 weeks I assure you. Water changes in the meantime>
My ammonia is 0ppm. My Nitrite is 0.25ppm, and my Nitrate is 40ppm. Before it was Ammonia 0, Nitrite 0, and Nitrate 40ppm and I read on the FAQs and all on WWM website, that the DSB would help get rid of the Nitrates or at least reduce it. But why am I getting a Nitrite rise (before the DSB it was 0ppm) and how long will the DSB take, if it does work, to reduce my Nitrates, and now the Nitrites??
<2 weeks or less... you can almost set your watch to it. Nitrate will be reduced>
By the way, I lost 3 of my damsels in the process of changing the substrate. I did move all the fishes to another container with a heater and an airstone and all until the sand settled in the main tank.
<heated vessel?>
2 of the damsels didn't last long in the container which had water from the main tank before putting the DSB in. I don't know why they died because after testing the water I found the Ammonia 0, Nitrite 0, and the Nitrate 40ppm (in the container).
<temp drop/shock oftentimes>
Now, after the DSB settled in the main tank and after testing the Main tanks water I got Ammonia 0, Nitrite 0.25ppm, Nitrate 40ppm, PH 8.0, and Salinity 1.022. So I put the fishes in and all of them are breathing heavily. I then lost another damsel. It's been 3 days now after introducing the fish to the main tank with the new substrate and the fish are still breathing heavily. Please help !!! What is happening ??? What do I do ??
Many thanks crew in advance... Regards, Ash  
<use heavy carbon in addition to doing several large water changes... something sounds amiss. A possible contaminant. Your chemistry is really not that bad at all! Best of luck. Anthony>

Deep (Sand Bed) Trouble!
Hi Crew ...
<Scott F. at the keyboard tonight!>
As always I would like to thank everyone at WWM for giving us hobbyists the support and knowledge we hobbyist are in great need of.
<Thanks so much for your kind words! We get a big a kick out of helping our fellow hobbyists-we all should share our experiences and learn together>
To my questions. I have put down a Southdown Tropical Caribbean play sand DSB of about 4 inches or so, on the bottom of my tank. God was it a hassle to get the sand to settle. But finally it did.
<Yep- a nasty process!>
My problem is that I have a clown fish that loves to dig. And almost everyday the clown makes a mess making the water all cloudy and takes almost a whole day to settle down again, the sand that is. I have a FO tank and I'm thinking of getting some LR, about 30lbs or so. What do I do to keep that clown from making such a mess?
<Well, unfortunately, there is no real great, guaranteed way to prevent the fish from engaging in this behavior. Nature is in charge! In fact, I can't really think of any way, short of moving the fish to a different...! Sorry about that one!
Another question if I may. My tank chemistry is out of whack after introducing the sand. My ammonia is 0ppm. My Nitrite is 0.25ppm, and my Nitrate is 40ppm. Before it was Ammonia 0, Nitrite 0, and Nitrate 40ppm and I read on the FAQs and all on WWM website, that the DSB would help get rid of the Nitrates or at least reduce it. But why am I getting a Nitrite rise (before the DSB it was 0ppm) and how long will the DSB take, if it does work, to reduce my Nitrates, and now the Nitrites??
<Well, the nitrite is not something we like to see, but it probably snuck up as a result of the increase in sand bed depth (perhaps some temporary interruption of the biological filtration process occurred). With routine maintenance and patience, it should quickly return to undetectable levels>
By the way, I lost 3 of my damsels in the process of changing the substrate. I did move all the fishes to another container with a heater and an airstone and all until the sand settled in the main tank. 2 of the damsels didn't last long in the container which had water from the main tank before putting the DSB in. I don't know why they died because after testing the water I found the Ammonia 0, Nitrite 0, and the Nitrate ppm (in the container). Now, after the DSB settled in the main tank and after testing the Main tank's water I got Ammonia 0, Nitrite 0.25ppm, Nitrate 40ppm, PH 8.0, and Salinity 1.022. So I put the fishes in and all of them are breathing heavily. I then lost another damsel. It's been 3 days now after introducing the fish to the main tank with the new substrate and the fish are still breathing heavily.
<Well, this could be anything from the obvious (i.e.; detectable nitrite level), to the bizarre (perhaps some silt or other compounds leaching from the Southdown (that escaped the rinse process), causing a shock reaction of some sort...Hard to say. If it were me, I'd get the damsels back out of there, if possible, and let the tank "re-cycle", which will probably take a week or two, maybe longer.>
Please help !!! What is happening ??? What do I do ??
Many thanks crew in advance...Regards, Ash   
<I think that a healthy dose of patience and careful monitoring of the tank chemistry is the best thing to do, at this point. Nothing really spectacular, just basic moves...Hang in there! Regards, Scott F>

DSB
Hi Bob (I hope it's Bob)
<Tis>
I just read your exchange with Steve Walker regarding the set up of his custom 825 gallon tank.
My question is this, with so much controversy over DSB lifespan, wouldn't it be wiser for him to go with a bare bottom or minimal sand?  He is going to have a large refugium with DSB and an enormous live rock capacity.  I am already worried about my barely cycled DSB giving up the ghost down the line and that's with just a 55 gal tank.  I would have a heart attack if I had to redo a 825!!!  Thanks and keep up the good work, I love this site.
Jerry
<Thank you for this... I suspect (strongly) that in the course of rinsing and placing all this sand and consequently the rock, that Steve will have plenty to think about re this possibility. Have actually seen much larger (public) aquariums with DSB's, plenums... Like many endeavors, there is correspondingly less work (relatively) with increasing size... not too hard over the course of a few good sized water changes to vacuum out a good part of the substrate with a good-sized diameter length of tubing. Bob Fenner>

DSB
Bob,
I appreciated Jerry's question, and your response.  I can't say I'm excited about rinsing 2000+ lbs of sand, but as you suggested, when it comes time to replenish/replace - I will always have the option to 'go thin'.  
<Yes>
To the question of DSB lifespan, it occurs to me that I have made a rather large assumption about my DSB design and I had better flush it out (no pun intended) sooner rather than later.  Am I correct in assuming/understanding that DSB lifespan is, in part, a function of its rate of dissolution?
<Yes>
  Or asked differently, if the rate at which the DSB dissolves is reduced, will it remain viable longer?
<Affirmative>
If this assumption is valid, is it reasonable to assume that I can reduce the rate of dissolution of the main DSB (1000+ lbs of sand) by adding a second large DSB (another 1000 lbs of sand) in the refugium(s)?
<Correct>
Could this strategy serve to extend the life of the main DSB by any meaningful amount of time (recognizing both DSBs will dissolve at an equal, but slower, rate)?  
<Yes, could easily double plus>
Anthony estimates in his book that the half life of the DSB is 18-24 months - hence the reason for my dreaming/scheming to find a way to extend the interval for what will certainly be a significant maintenance event.
<I agree with this value and your concern/thinking. Bob Fenner>
Thanks again for your thoughts.
Steve  

DSB
I was inclined to use a deep sand bed until I heard the following horror story:
"Yes, I have read Shimek. He should have been there when we recently took down and re-set up a reef tank in a large trading company office with only a 4 inch bed of fine aragonite. The tank had been set up by another company and was wiped out because the company servicing the tank had sent an inexperienced person to clean the tank, and they accidentally stirred up the bottom a little too much. When we arrived, there was no odor, but when we got the water down and started to remove the gravel, the smell was so powerful, they had to close the office and send everybody home because you couldn't open the windows, and two of us got very sick. It smelled like a sewer. You may very well be successful with a DSB as you will not be hands-off and will care for the aquarium better than the clients for whom we manage aquaria."
Any thoughts as to whether I should indeed be discouraged?
<Nope, I find the story hard to believe. Even if it was true, the "bad" service company may have been doing a whole host of things wrong (incorrect grain size, lack of sand fauna, sand critters predators, overfeeding, lack of nutrient export, etc.) that led to these problems.>
If a DSB is the way too go, what is the preferred substrate?
<Fine grain size>
I see that many people use the Southdown play sand from Home Depot. Why?
<Because it is aragonite material and very cheap.>
What about just using all Aragamax?
<That is fine, too. -Steven Pro>

Re: DSB Crash
Yes I did - and I could have missed it I guess, but I was attempting to address the SPECIFIC issue of the lifespan of a DSB being 2-3 years and then it crashes, killing everything in the tank.  Is this true?
<Not in my experience. I am a fan of monthly "stirring", annual replenishment (including upper layer disruption) of such substrate arrangements though>
I mean it does kind of makes sense I guess sense all that waste has to go somewhere... is there some method of cleaning it to extend the lifespan?
<Oh! Yes... as stated, though I would not thoroughly gravel vacuum the substrate, I would stir it with a dowel (wood or plastic) on a regular basis, and add more material to it every year (you'll find it "goes away" as in dissolves over time).>
Sorry for the trouble  :o)
<Me too. No worries. Just trying to get to an answer. Bob Fenner>

Deep Sand Bed
Cheers, Samuel! > Hi, Mr. Calfo, > > Your book is great. Mine is a bit worn now because > it > has been read a lot. Wow! Now that's a compliment. I thank you kindly and I am delighted to hear it! > > I am thinking of having a deep sand bed (6 inches) > in > my aquarium. Yes...6+ inches is my preference. What do you think of the idea of adding sand in an aquarium one layer (about two inches) at a time so as to allow the previous layer to mature and to be populated by the desired organisms and bacteria before adding the next layer? Definitely a problem as the intermediate stage of 1-3 inches in particular will struggle as a zone too deep to be sufficiently aerobic and not deep enough for anoxic activity. This is the root cause for many critics complaint about DSB methodologies... they don't put a deep enough sand bed for either strategy to succeed and the sand bed (at 1-3") becomes a dead zone and nutrient sink. > > I wonder if a one-time addition of 6 inches of sand bed will cause the lower portion of the bed to be too  much anaerobic and thus it will create hydrogen sulfate. Rest assured, a well maintained aquarium will have no such problem. I have moved many displays in the last decade that never ceased to amaze me... after years of being set up, the sand shoveled out of the aquarium looked like it was brand new! Sulfides occur from neglect of husbandry (poor water circulation in display, a skimmer that doesn't produce daily, overfed or overstocked with fish, lack of detritivores, etc). Some keys to success: all fine/sugar fine sand grains (never mix grades especially with course sand), always have very good water flow in display with minimal dead spots, over 4" must be maintained everywhere at all times, resist too many hermit crabs and rely on more gentle detritivores (White sand stars, sea cucumbers, etc). Gentle stirring of the sand on occasion is optional but may help some coral species (like Nephtheids). > > Thank you very much for your time. > > Cheers, Samuel Best regards, my friend. Anthony

Crashing DSB System.  HELP!!!  07/02/05
I've got a Deep Sand Bed set up in my refugium which I think is going to crash soon!!!
<... what?>
Setup:  Sand bed is about 6-7 inches deep.  Grain size is about 2mm.  Macro algae on top of DSB for added filtration. Sand is put directly on bare bottom of tank. Where I live, DSB is not common.  Thus, the 2mm sand is about the finest that I can get!!!  I do get lots of tiny bubbles in the top layer of the sand, which means that it is working to a degree.
<Yes...>
Some background info first.  I dismantled my tank when I shifted house 3 months ago.  My previous setup was DSB with a plenum in the main tank. Being adventurous with my new setup, I removed the plenum, and went without.  The sand from my previous setup is used.  After being used for 5 years in the old set up, you can only imagine how dirty the sand was!!!  Anyway, I cleaned the sand as best I could, and re-used it for the new setup.
<This can be a bit risky>
  I think lot of featherworms were buried in the process, and I think that is one cause for my problem.  Very quickly, the sand is now inhabited with worms and pods again.
<Ah, good>
Just 1 hour ago, I was harvesting some algae with roots 2 inches into the sand bed.  When I pulled out the roots, the sand that came out with it was black!!!  Hydrogen Sulphide!!!!
<Mmm, or other oxidized material...>
As a test, I syphon with a gravel cleaner deep right to the bottom of the tank in a few places.  (I know, I am NOT supposed to disturb the sand bed...
but I am currently quite desperate!!!)  Out came BLACK WATER!!!  The smell confirms that I have Hydrogen Sylphid!!!  
<You did the right thing by vacuuming, testing...>
I think it is not at a critical level yet ... as in the smell is weak, and the sand close to the glass looks white (only the middle portion is affected). I read somewhere that Hydrogen Sulphide is toxic only at a very high concentration, so I am safe for the moment.  I remember reading somewhere long time ago which says to leave it alone, and it will go away.
<Mmm, actually, I don't agree here. I would continue to gravel vacuum the DSB when you're doing water changes>
I wonder if the roots of the macro algae has anything to do with this!!!
<Mmm, not much>
What do I do next?? Should I disconnect with the main tank? Should I dismantle the setup, and thoroughly clean the entire sand bed??? Should I just wait and see??
<I'd continue to gravel vac as mentioned, just keep your eye on your livestock...>
I was given the advice to scrap my DSB as my sand particle is too big for it to work . but if it is too big, why am I getting Hydrogen Sulphide in the first place???
<Don't fear the H2S... Bob Fenner>

Re: Crashing DSB System.  HELP!!! 7/4/05
Dear Bob,
<Jason>
Thanks man!!! Now I can sleep better!!
<Ah, good>
As the DSB is separate from the main tank, it will be quite painless for me to clean up the sand again.
<Thank goodness for good planning>
I just hate "re-start" the system again after 3 months of waiting!!!  But I agree ... it is a small price to pay for long term stability!!!
Jason
<Cheers, Bob Fenner>