DSB Heresy

[thriceanangel]

I am not planning on removing 5 gals. Much more than that, and it will flow into the closed loop system. Should check out the link I've posted for more info on what I am experimenting with.

I have removed more than a few sand beds for various reasons, and there is ALWAYS foul smelling detritus gunk at the bottom. It's a filthy mess that you can't be seen through because it's basically mud. Not fine sand by any stretch of imagination. Not just my tanks either, so it's not just me.

 

[salty joe]

[i I have removed more than a few sand beds for various reasons, and there is ALWAYS foul smelling detritus gunk at the bottom. It's a filthy mess that you can't be seen through because it's basically mud. Not fine sand by any stretch of imagination. Not just my tanks either, so it's not just me. [/B]

Ditto that.

 

[SPC]

There shouldn't be any "gunk" in the sand, whether you have a plenum or not, even after years of use.

Could you explain how it is possible to not have any "gunk" in a DSB?

Steve

 

[thriceanangel]

I think it's one of the reasons that many people elect to go BB, because people think that is a big nitrate producer. BB systems supposedly blow it around where it can be filtered out mechanically, or eaten by corals... or at least thats the theory

 

[carlso63]

<a href=showthread.php?s=&postid=10202738#post10202738 target=_blank>Originally posted</a> by thriceanangel
Thing of it is that when you're removing 5 gals per day, you are only removing the water immediately surrounding what ever intake you have. If my plenum is one inch deep it holds 10 gallons. This also goes on the theory that has been discussed earlier in this thread, that a certain amount of dissolved o2 will not destroy the denitrification of anaerobic denitrifiers. BUT I still am under the assumption that MOST of the water will be drawn from the 2 above sand intakes, slowing the flow through the below sand intakes. I wouldn't say that it rapid draining of the plenum.
I am not opposed to a deeper sand bed either. 7" isn't out of the realm of possibility. However anyone who has removed a sandbed knows that there is TONS of built up gunk down there, am I to believe that just because there is a plenum that there wouldn't be for some reason?

<a href=showthread.php?s=&postid=10202738#post10202738 target=_blank>Originally posted</a> by mr wilson
You haven't explained the prupose of removing the 5 gallons, or what you do with it.
I agree that a small influx of oxygen will not harm denitrifying bacteria. In fact, bacteria goes into lag phase where it increases in numbers with environmental changes, such as temperature, salinity, and changes in D.O. levels. It's a natural defense mechanism.
There shouldn't be any "gunk" in the sand, whether you have a plenum or not, even after years of use. Most of the debris in the plenum will be fine sand, with a small amount of detritus. Perhaps you are mistaking this fine sand as "gunk".
There's no problem with a 7" deep sand bed, as long as you have at least 4" of viable anaerobic zone.
The idea of a passive flow through the sand has its' merits. I use a perforated PVC pipe placed vertically in the sand to provide a passive water exchange, and means for nitrogen gas release. A heat source below the sand, such as a refugium light, would be the most efficient means of passive flow. A thermal exchange would occur as the heat rises.

It seems to me that any kind of "active flow assistance" involving manipulation or fluid motion of the plenum water is going to defeat the purpose of a plenum in the first place... certainly with any kind of "gallons per hour" movement IMO a plenum will not perform properly.

As far as the issue of "gunk" in sandbeds, it is almost always related to the formation of, and production of H2S (hydrogen sulfide) due to total lack of free oxygen availablitly. This is a fairly common problem with a DSB and again, IMO, all DSB applications greater than 5" will see some H2S formation... can range from almost unnoticeable (darker patches inside the sandbed that smell alittle "funky" upon removal) to problematic and chronic (a tank that smells like 'rotten eggs' and experiences unexplained die-offs or 'crashes')... in any event I have yet to see a teardown of an established DSB that was 100% H2S free.

The reason that this is not an issue running a plenum has to do with circulation available at the very lowest region of the bed - a plenum has a void space of only water at bottom, which does experience some obvious (though slow) circulation; whereas a DSB has substrate the entire depth, hampering circulation and if the entire sandbed is sugar-grained size the bottom layers tend to get compacted over time - as well as depth of the sandbed itself (in general, a DSB is often several inches 'thicker' than a plenumed bottom)...

The most recent issue of Marine & Reef magazine has a very interesting article plenums involving the Waikiki Public Aquarium in Hawaii. In particular, analysis of several very large plenumed reefs compared to similar reefs running with a DSB. Interesting to note that upon teardown there was evidence of H2S in all the DSB reefs, yet none of the plenumed reefs had any traces whatsoever. And this from a professionally managed series of extremely large setups...

I would just add that while I don't see the harm of CPW I also have yet to see any advantages - other than the tandem ideas of removing what should be the most "polluted" water for water changes and the possible advantages of small, daily water changes vs. larger, less frequent ones...

 

[thriceanangel]

Nope, I'm familiar with the hydrogen sulfide and it's lovely accompanying smell. And it's not even only in DSB's, I've seen it in 1" of sand. AS far as this method I'm proposing all's I can say is we'll see.

 

[mr.wilson]

I guess it's a husbandry issue, as I haven't had these problems.

I use sand sifting inverts and fish and run a closed loop on my tanks, so that may be why. I can see a tank with powerheads and no sand sifters having a detritus build-up issue. A low redox potential would cause these issues. Sugar fine sand may also be the cause.

In this article Randy Holmes Farley discusses hydrogen sulfide, and provides some tests of his 10 year old reef tear down. In it he finds no hydrogen sulfide, no major detritus deposits, and only a minor amount of iron sulfide.

http://reefkeeping.com/issues/2005-12/rhf/index.php

 

[thriceanangel]

A very interesting article. Not really pertinant though because as I already stated, I'm not talking about H2S.

I have sand sifters too, and most everyone I know does as well. However, most people I know still have this buildup which isn't apparent unless you stir the bed, vacuum it (which wouldn't be needed unless there was something to vacuum) or remove it. I have had it with a crushed coral bed, and a more typical grain of aragonite. I guess you might not have it if you vacuumed the bed almost every day, but I think you'd still have areas that would get the gunk. It's not even really a husbandry issue either because I have removed a sand bed that was for all intents and purposes new. It was because too much flow was in the tank, and the sand had all rolled into one side of the tank. So there was a change to a more heavy grain after about 2 weeks. The sand still had a bit of muck given the short life of the sand bed. Keep in mind that I am NOT talking about black sediment indicating H2S. In fact, again it isn't visible until you stirr, vacuum, or remove the bed. So I don't know how you don't seem to have this, and Randy doesn't seem to even address what I am talking about, but kudos to you, you don't have to worry about it.

When was the last time you removed a sand bed?

 

[mr.wilson]

I get hired to move a few reef tanks a year. Most of the time, there is a new, larger tank being set-up, so new sand is added. I also get a few upgrades where someone wants everything moved to a larger tank in the same location. Most reef tanks I encounter have more detritus in the rock, than in the sand.

I used to remove the top 1" of sand annually to get rid of bound phosphate and silicates, until iron-based absorption media came on the market (Phosban/Rowaphos).

I did a 25% water change in a 220 gallon tank a few months back. I started vacuuming the 4" sand bed, but stopped after a few minutes, as there wasn't much to remove.

Over the years, I've vacuumed tanks that get an incredible amount of detritus in just a month, but they were problematic tanks with poor husbandry (over-feeding) and flow dynamics (powerheads at the top of the tank).

Do you use a mechanical filter? Pleated cartridge, polyester fiber or 100 micron filter bag?

If you can't eliminate detritus through the common methods, then your idea will work.
Your closed loop plenum will create an aerobic zone in the substrate that will allow heterotrophic bacteria to break down your detritus build-up.

It would be more efficient as a reversed flow under gravel filter as it would migrate detritus back up into the water column, where it can be mechanically removed. It would also foster the growth of detritus consuming aerobic bacteria. The resulting increase in ORP, would discourage the formation of hydrogen sulfide.

You would have to employ a remote sand bed or sulphur-based denitrifier to remove the influx of nitrate. A pleated cartridge filter such as the Ocean Clear, or Pentair/Lifeguard would have to be used to avoid further detritus clogging.

The problem with a closed loop in the plenum is it only moves detritus from the plenum to the water column. The detritus you are moving must first travel through your deep sand bed before it can be removed. By the time the detritus makes it to the plenum, it may be basically inert. You would be better off siphoning the sand every month or so when you do water changes.

I've never used sugar-fine sand, but I have found that silica sand doesn't allow detritus to settle below the surface. Perhaps this would be a sufficient barrier for you.

 

[thriceanangel]

Right now, while I am currently building the tank, I am running a small (smaller than anything I have ever had) 29 gal bowfront. It currently doesn't have a closed loop, but it has the high flow MJ Mod -around 2000 gph, I have a 20 gal sump with Chaeto, and live rock with a mag 5 creating the through sump flow. On top of the MJ Mod, in the tank I have a MJ 1000, and an aquaclear 400 gph model. I think that there is probably adequate flow.

I feed a pinch of food a day to the following stock:
1 clarkii
1 firefish
3 small chromis
1 med royal gramma
1 coral beauty

Maybe a tadd overstocked, but not too bad.

Cleanup crew:

Red Leg Hermits
3 Dove snails- sand sifters
Margarita snails
1 Emerald crab
blue leg crabs

About 40 lbs of LR in tank
with another 20 or so in sump

I have about 5" of 1mm grain aragonite sandbed
a protein skimmer
Filter sock - not sure the size
use only RODI water and currently change 8 gals weekly.
I dose Kalk in replacement RODI water.
Passive activated carbon/denitrate mix

How is the husbandry bad? What am I missing? I still have the gunk when the sandbed is stirred. It will definately cloud the tank.

I doubt that the detritus that reaches the plenum will be inert, it may be mostly broken down, but thats the point. It won't sit under/in the sand and rot. It will be blown back into the tank to be mechanically filtered out or if nothing else a second pass at the sandbed.

But I would again suggest that you read at least the beginning of the thread to see what the guy was talking about. I think that he was on to something, but it needed to be refined a bit.



I am however interested in the reverse flow idea, I'll have to give it some thought.

 

[mr.wilson]

Sorry, I don't want to come across as critical. You wouldn't be making this kind of effort if you didn't have the best intentions.

The only thing I would change with your practices to avoid detrital build-up is the flow pattern. Flow rates are rarely a problem, it's the pattern that counts (quality not quantity).

Powerheads and Aquaclears tend do dump heavier particles on the substrate. A closed loop system (or well placed powerheads) will keep detritus suspended until it's picked up by the Aquaclear, filter sock or protein skimmer. The flow needs to directed across the bottom, then up, in a circular pattern.

MJ mods are great for flow volume, but they don't achieve all of the criteria of good flow dynamics (suspension, surface skimming, and gas exchange).

As far as sand sifters go, you will see a world of difference if you have a pair of valenciennea sps. gobies (Wardi/Tiger, Puellaris/Diamond, or Strigata/Goldhead). Brittle stars and serpent stars are less significant, but useful. Nassarius and stomatella snails are two more I don't see on your list. A healthy population of bristle worms are also invaluable. This is why "new" tanks get a detrital build-up.

Yes, they will disturb the DSB, but the detritus they reduce and remove is far more important than secondary nitrate reduction. If they out-compete with heterotrophs, then nitrate is less likely to accumulate.

There are a couple of old timers here on RC with Reverse flow UGF's that have been running (successfully) for decades.

 

[thriceanangel]

Here is from the first post:

1. It assumes the fluids in the bottom of a DSB are anoxic and are not fully stabilized.

2. It assumes anoxic waste can buildup at a faster rate than the available bed active biological surface can fully stabilize it.

3. It is designed to remove unprocessed or reconstituted nitrates, nitrites, ammonia, phospahtes and other organic waste that accumulates in the bottom of the bed.

4.It assumes DSB and Jauberet designs are not 100% effective in biological stabilization, and infact do cause a major build up of anoxic Hydrogen Sulfide in the bed that does and can leak back into the tank.

5. It is simply a method to compensate for this inefficiency.

6. It improves the DSB biological efficiency by moving fresh food into the zones.

I'd focus on #2 and his solution was to take small amount out and drain it. My solution is to contantly drain it and recirculate it into the tank either to be flitered out, eaten, or pass through the sandbed again.

You may disagree with this listing, and think that a DSB works fine in a nominal state and it may for you. But for whatever reason, it can be catasptrophic and cause a crash if something is out of balance. This may be a solution, or it may not. Time will tell.

 

[thriceanangel]

Yeah I've read all about Paul B's tank! It kind of defies reason.

Forgot to add the bristle worms, and stars are all over because I didn't buy them

The MJ Mod in a 24" tank creates flow everywhere, Really everywhere. Doesn't really matter if the aquaclear drops stuff because it doesn't get very far before it is in a vortex. The flow hits the other side of the tank, and goes up (creating turbulence) and down across the bottom, then up the other side (in general). There are constant eddies and vorteces caused by the other powerheads.

 

[mr.wilson]

<a href=showthread.php?s=&postid=10217678#post10217678 target=_blank>Originally posted</a> by thriceanangel
Here is from the first post:

1. It assumes the fluids in the bottom of a DSB are anoxic and are not fully stabilized.

2. It assumes anoxic waste can buildup at a faster rate than the available bed active biological surface can fully stabilize it.

3. It is designed to remove unprocessed or reconstituted nitrates, nitrites, ammonia, phospahtes and other organic waste that accumulates in the bottom of the bed.

4.It assumes DSB and Jauberet designs are not 100% effective in biological stabilization, and infact do cause a major build up of anoxic Hydrogen Sulfide in the bed that does and can leak back into the tank.

5. It is simply a method to compensate for this inefficiency.

6. It improves the DSB biological efficiency by moving fresh food into the zones.

I'd focus on #2 and his solution was to take small amount out and drain it. My solution is to contantly drain it and recirculate it into the tank either to be flitered out, eaten, or pass through the sandbed again.

You may disagree with this listing, and think that a DSB works fine in a nominal state and it may for you. But for whatever reason, it can be catasptrophic and cause a crash if something is out of balance. This may be a solution, or it may not. Time will tell.

I don't think these points have been proven anywhere in this thread.

Your idea certainly warrants exploration for other reasons however.

 

[thriceanangel]

No not proven, but theorized.

 

[mr.wilson]

<a href=showthread.php?s=&postid=10217922#post10217922 target=_blank>Originally posted</a> by thriceanangel
No not proven, but theorized.

I guess it shouldn't bother me. Theories are always more interesting than known facts.

 

[SPC]

<a href=showthread.php?s=&postid=10216927#post10216927 target=_blank>Originally posted</a> by mr.wilson
I get hired to move a few reef tanks a year. Most of the time, there is a new, larger tank being set-up, so new sand is added. I also get a few upgrades where someone wants everything moved to a larger tank in the same location. Most reef tanks I encounter have more detritus in the rock, than in the sand.

Have these tanks had vacuuming of the sand, sand stirrers etc... employed, or were they run like the DSB method that Dr Ron uses (which is what the vast majority of us used when setting up a DSB)? What type of sand was used? How old are these tanks?

I used to remove the top 1" of sand annually to get rid of bound phosphate and silicates, until iron-based absorption media came on the market (Phosban/Rowaphos).

I don't understand how the use of Phosban would help here, Mr Wilson? Are you running the Phosban in some location other than the main tank?

I did a 25% water change in a 220 gallon tank a few months back. I started vacuuming the 4" sand bed, but stopped after a few minutes, as there wasn't much to remove.

I just vacuumed my 2 month old SSB (3" or so) and found plenty of reason (detritus) to vacuum it.

Over the years, I've vacuumed tanks that get an incredible amount of detritus in just a month, but they were problematic tanks with poor husbandry (over-feeding) and flow dynamics (powerheads at the top of the tank).

I agree 100% with you that husbandry plays a huge part in this, but just the nature of sand will place limitations on this. For example, I currently am at the maximum of flow, any more and the sand will be carved out to the bottom glass and piled up in other areas. This is not a unique problem however, experienced reefers have been looking for this magic flow rate for years now.

Do you use a mechanical filter? Pleated cartridge, polyester fiber or 100 micron filter bag?

I use a 100 micron filter bag, but this dosen't help with some (maybe 50%?) detritus and food that gets to the SSB.

If you can't eliminate detritus through the common methods, then your idea will work.
Your closed loop plenum will create an aerobic zone in the substrate that will allow heterotrophic bacteria to break down your detritus build-up.

How does the phosphate get out of the plenum (DSB)?

It would be more efficient as a reversed flow under gravel filter as it would migrate detritus back up into the water column, where it can be mechanically removed.

If this is true, then how does a passive DSB/SSB accomplish this?

The problem with a closed loop in the plenum is it only moves detritus from the plenum to the water column. The detritus you are moving must first travel through your deep sand bed before it can be removed. By the time the detritus makes it to the plenum, it may be basically inert. You would be better off siphoning the sand every month or so when you do water changes.

I agree.

I've never used sugar-fine sand, but I have found that silica sand doesn't allow detritus to settle below the surface. Perhaps this would be a sufficient barrier for you.

I am using pool filter sand in my 2 month old SB, but I haven't observed less detritus build compared to my original 3 year old sugar fine aragonite 5" DSB?

Steve

 

[thriceanangel]

Usually, but sometimes there's nothing to it. I'm just seeing how well it works, and if it's an improvement over the traditional DSB over time. It's not scientific at all, there will be no control group. Just an anecdotal "It works great for me." No reason to get bothered by it though. Just an attempt at an improvement, based loosely on water filtration techniques and sewage treatment, on something that for whatever reasons hasn't worked for everyone. If it works for you, then thats great! Paul B's filtration works great for him obviously. Could it be improved? Will it work for everyone? Is it the best way? Those are questions best answered individually.

 

[SPC]

<a href=showthread.php?s=&postid=10217621#post10217621 target=_blank>Originally posted</a> by mr.wilson
Sorry, I don't want to come across as critical. You wouldn't be making this kind of effort if you didn't have the best intentions.

The only thing I would change with your practices to avoid detrital build-up is the flow pattern. Flow rates are rarely a problem, it's the pattern that counts (quality not quantity).

Powerheads and Aquaclears tend do dump heavier particles on the substrate. A closed loop system (or well placed powerheads) will keep detritus suspended until it's picked up by the Aquaclear, filter sock or protein skimmer. The flow needs to directed across the bottom, then up, in a circular pattern.

...and again, you are the first reefer I have seen accomplish this flow pattern in a SB tank that can keep all the detritus in suspension. Heck, I just got finished running a BB tank that I couldn't keep all the detritus in suspension.

As far as sand sifters go, you will see a world of difference if you have a pair of valenciennea sps. gobies (Wardi/Tiger, Puellaris/Diamond, or Strigata/Goldhead). Brittle stars and serpent stars are less significant, but useful. Nassarius and stomatella snails are two more I don't see on your list. A healthy population of bristle worms are also invaluable. This is why "new" tanks get a detrital build-up.

If this is the cure for a build up in a DSB, how is it that DSB's in nature (low flow and high organic like our little closed systems) go eutrophic, or are you saying that the flow rate and nutrient load of your tank more closely approximates the sand around a reef?

Yes, they will disturb the DSB, but the detritus they reduce and remove is far more important than secondary nitrate reduction. If they out-compete with heterotrophs, then nitrate is less likely to accumulate.

How about the accumulation of phosphate?

There are a couple of old timers here on RC with Reverse flow UGF's that have been running (successfully) for decades.

Well we might as well include more of the story here, if one of these people is Paul? You know that he has said in the past that he has a piece of asphalt in his tank, don't you?

Steve

 

[mr.wilson]

<a href=showthread.php?s=&postid=10218195#post10218195 target=_blank>Originally posted</a> by SPC
Have these tanks had vacuuming of the sand, sand stirrers etc... employed, or were they run like the DSB method that Dr Ron uses (which is what the vast majority of us used when setting up a DSB)? What type of sand was used? How old are these tanks?[/i]

Most would have sand stirrers, and medium to coarse sand. I think DR. Ron is framing it as the most efficient way of developing denitrifying bacteria, and not necessarily the most efficient way of running a tank.

Things go wrong when only portions of someone's recipe for success is used. I'm sure a means of detritus suspension was advocated by Dr. Ron. I assume Dr. Ron doesn't have detritus build-up in his substrate.

I certainly don't doubt that many people get vast detritus deposits, as I've dismantled these tanks many times. I haven't however, seen a successful tank that had significant build-up in the sand. I attribute this to a high redox potential, good nutrient export & mechanical filtration, proper flow dynamics for detritus suspension and removal, and sand sifters.

A tank with true sand sifters (not just stirrers) will not require any maintenance to the sand bed. Once again, you will lose some biofilms as a result, but to the greater good of the aquarium. Reef tanks devoid of sand sifters will have algae blooms in the sand, and detrital accumulations.

I don't understand how the use of Phosban would help here, Mr Wilson? Are you running the Phosban in some location other than the main tank?

The phosban is located in the sump. As phosphate is removed from solution, phosphate is leached from calcareous media. The substrate is no longer need as a passive adsorption media.

I just vacuumed my 2 month old SSB (3" or so) and found plenty of reason (detritus) to vacuum it.

A new tank will have difficulty breaking down organics as quickly as they form. You may have a different success rate after a year of bacterial and benthic invertebrate development.

I agree 100% with you that husbandry plays a huge part in this, but just the nature of sand will place limitations on this. For example, I currently am at the maximum of flow, any more and the sand will be carved out to the bottom glass and piled up in other areas. This is not a unique problem however, experienced reefers have been looking for this magic flow rate for years now.

As I stated earlier, it's not a magic flow rate, but a flow pattern (quality rather than quantity). I find 15 to 20 times the volume of the tank to be adequate if the flow pattern is correct. You may have conflicting flow patterns that cause swirling motions to trap detritus on the bottom. A tank 40 times the volume turnover, with chaotic flow patterns will surely be problematic.

I use a 100 micron filter bag, but this dosen't help with some (maybe 50%?) detritus and food that gets to the SSB.

Your water flow should be able to remove all traces of flake food from the tank in 10 minutes without any settling on the substrate. Floating flake food should be collected by the overflow within 60 seconds without sinking (unless caused by fish).

How does the phosphate get out of the plenum (DSB)?

Phosphate binds to calcareous media, and is not freely floating around the plenum, to any extent greater than the phosphate readings of the display tank water. As phosphate is removed from the water column, more phosphate will leach from the DSB.

If this is true, then how does a passive DSB/SSB accomplish this?

My comment was that it (RFUGF) would be a more efficient sand bed for your needs, which is detritus deduction. A static sand bed is for nitrate reduction, not detritus reduction. It's difficult to do both well at the same time.