DSB Heresy

[mr.wilson]

<a href=showthread.php?s=&postid=10218384#post10218384 target=_blank>Originally posted</a> by SPC
...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.[/i]

The TOTM is full of such tanks. heavy detrital build-up may be commonplace, but it isn't inevitable. You will be hard pressed to find a succesful tank that is plagued with detritus build-up issues. Siphoning and sand replacement isn't the key to their successes.

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?

I wasn't aware that natural reefs went eutrophic due to detrital build-up in the substrate.

How about the accumulation of phosphate?

I don't think phosphate accumulation is a problem for users of Phosban or Rowaphos etc. Phosphate is a surfactant that readily goes into solution as space becomes available for it in bulk water.

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?

What's wrong with asphalt? Does he have a nuisance algae problems, nitrate issues, or detritus build-up?

 

[salty joe]

All this talk about clean and dirty substrate and no mention of advection???

 

[mr.wilson]

<a href=showthread.php?s=&postid=10231396#post10231396 target=_blank>Originally posted</a> by salty joe
All this talk about clean and dirty substrate and no mention of advection???

Alright, I googled "advection". In what respect do we apply the principal here?

 

[salty joe]

As explained by Delbeek and Sprung in "The Reef Aquarium Science Art and Technology", (quote) "If you have any any water movement, the water moves into the sand"

It is explained in detail in the book.

 

[salty joe]

< If you have any any water movement, the water moves into the sand"

. [/B]

Should read:

If you have any any water movement, the detritus moves into the sand"

 

[pjf]

DSB Goals

DSB Goals

Before we argue about what methods are best suited for sand bed maintenance, we should clearly state our goals. Are we trying to: (1) use an anoxic DSB for nitrogen export, (2) use an aerobic sand bed to drive the nitrogen cycle, or simply use the sand bed as an ornament?

The goal of traditional DSB’s is the reduction of nitrates into nitrogen gas by nurturing anaerobic bacteria. This approach avoids the use of large sand sifters that could disturb the denitrifying bacteria. The fine grain size of the sand is chosen to resist detritus and cleanup crews are used to mop detritus from the surface. The nitrates to be reduced are produced by aerobic bacteria in live rock and in the oxygenated upper layers of the sand bed. Nitrogen is exported as N2 gas.

By adding sand sifters to a sand bed, we are giving up on anaerobic nitrate reduction. Instead, we may be using the sand bed to nurture only aerobic bacteria to drive the nitrogen cycle. Ammonium is converted into nitrates to be exported by other means: macro algae filtration, sulfur reactors, or water changes.

If the goal is simply to maintain a sand bed as ornamentation, there is not a whole lot to argue about in this thread. We can simply siphon the nitrates and sulfides from the bottom of the DSB as suggested by the originator of this thread.

 

[mr.wilson]

Re: DSB Goals

Re: DSB Goals

<a href=showthread.php?s=&postid=10246490#post10246490 target=_blank>Originally posted</a> by pjf
Before we argue about what methods are best suited for sand bed maintenance, we should clearly state our goals. Are we trying to: (1) use an anoxic DSB for nitrogen export, (2) use an aerobic sand bed to drive the nitrogen cycle, or simply use the sand bed as an ornament?

The goal of traditional DSB’s is the reduction of nitrates into nitrogen gas by nurturing anaerobic bacteria. This approach avoids the use of large sand sifters that could disturb the denitrifying bacteria. The fine grain size of the sand is chosen to resist detritus and cleanup crews are used to mop detritus from the surface. The nitrates to be reduced are produced by aerobic bacteria in live rock and in the oxygenated upper layers of the sand bed. Nitrogen is exported as N2 gas.

By adding sand sifters to a sand bed, we are giving up on anaerobic nitrate reduction. Instead, we may be using the sand bed to nurture only aerobic bacteria to drive the nitrogen cycle. Ammonium is converted into nitrates to be exported by other means: macro algae filtration, sulfur reactors, or water changes.

If the goal is simply to maintain a sand bed as ornamentation, there is not a whole lot to argue about in this thread. We can simply siphon the nitrates and sulfides from the bottom of the DSB as suggested by the originator of this thread.

I think everyone has a different dynamic to their tank with different needs.

A system that is plagued with detrital build-up needs a system of avoiding (through proper flow) or removing detritus (sand sifters). You have to look at the cause and effect, and focus your resources where they are most effective. A well established colony of denitrifying bacteria is of little use when the demand is so high (due to excessive amounts of detritus).

A system that has low to moderate detrital build-up needs a sand bed for the purpose of nitrate reduction.

The focus of this thread is alternative methods of detrital export & assimilation. Before you reinvent the wheel, you need to make sure that you are using the current detritus export methods available, or you're just adding a fifth wheel.

 

[pjf]

If detritus on a DSB is the issue, wouldn't a clean-up crew to "mop" the surface of the substrate be the answer? I would think that large sand sifters, such as Sleeper Gobies, will drive the detritus deeper and disturb the anerobic conditions necessary for converting nitrates into N2 gas.

Even if the purpose of the sand bed is the aerobic conversion of ammonium into nitrites and nitrates (nitrogen cycle) for later export, isn't sand sifting likely to trap detritus deeper into the substrate and turn it into a nutrient sink?

 

[salty joe]

Hey BigDaddy,
I now realize the test for total phosphate is real expensive-what a drag. Is there any chance you could test for nitrite and ammonia?

Thanks for all the info you share.

Joe

 

[Steve 926]

Ditto on the info Big Daddy. :thumbsup:

Steve 926

:smokin:

 

[seabrookian]

Forgive me for not reading this entire thread, though I have read the majority of it. I do like this idea for the same reasons that 99% of others have already mentioned.

My question... someone early on mentioned that a similar idea was attempted, with the modification of taking a small, constant flow rate of waste off the bottom of the tank as opposed to flushing.

To me, a constant "drip rate" off the bottom still seems a good idea.

As a thought experiment... If the bed were being viewed as the "reactor" as stated earlier, then the i'd envision scaling the drip rate to a ORP or pH delta between the water column and the waste stream. I spent a bit of time the other day looking for ion selective electrodes hoping for a better option than ORP or pH, but did not but did not find a good combination of cheap & effective.

thanks,
Porter

 

[mr.wilson]

<a href=showthread.php?s=&postid=10262993#post10262993 target=_blank>Originally posted</a> by seabrookian
Forgive me for not reading this entire thread, though I have read the majority of it. I do like this idea for the same reasons that 99% of others have already mentioned.

My question... someone early on mentioned that a similar idea was attempted, with the modification of taking a small, constant flow rate of waste off the bottom of the tank as opposed to flushing.

To me, a constant "drip rate" off the bottom still seems a good idea.

As a thought experiment... If the bed were being viewed as the "reactor" as stated earlier, then the i'd envision scaling the drip rate to a ORP or pH delta between the water column and the waste stream. I spent a bit of time the other day looking for ion selective electrodes hoping for a better option than ORP or pH, but did not but did not find a good combination of cheap & effective.

thanks,
Porter

A dissolved oxygen meter would be the tool of choice for this kind of system. I use a Pinpoint unit that seems to work well, and doesn't cost much. It isn't available as a controler, but you could use it as a reference and set your flow rate accordingly.

 

[Serioussnaps]

Longest thread ever with the fewest pics.....stimulation underload dangit

 

[kolokefalo]

eutrophic reef

eutrophic reef

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?

Eutrophic "reef" regions are primarily lagoon areas where flow is the predominating issue with not being able to export nutrients, not the depth of the sand bed in these areas.

I am never a fan of the comparison between natural reef flow and flow in an aquarium. We can mimic it as best as we can, but in the end no matter what we are cycling the same water over and over and over. Since we are doing so we can't afford to try to mimic nature too much and create top to bottom flow....which is what most people do. Since our primary means of export of detritus and DOCs is by surface skimming we should try to create bottom to top flow.

You can see it in almost every FTS. The powerheads are at the left and right top back of the aquarium. 2 are aimed at each other, and the other 2 are bouncing off the front glass. By doing so it is creating a flow for detritus to become compacted into the sand bed. This effect can be reduced with excellent husbandry however, having the left powerheads blow across the bottom and the right across the top (or vice versa) will always provide you with a far less problematic microhabitat of a reef.

In nature the current is either surge or chaotic or both. It is rarely laminar, which is what a powerhead provides. Aiming them at each other can create a somewhat chaotic motion however while a top to bottom rotational cycle more closely reflects the surge current by waves and such it is counter productive in a closed environment due to our primary means of nutrient export (surface skimming).

btw this is an awesome thread.

 

[token]

I set up two DSB's with plenums almost six years ago. I am now in the process of moving. As a result, my smaller tank now houses all my rock and the larger tank and its DSB/plenum have been dismantled and moved.

As a result of this, I was able to see for myself the condition of my DSB/plenum. The DSB/plenum was the floor of my sump, 2.5" of PVC under a layer of fiberglass cloth over "egg crate" with 4" of aragonite over all of this. I used 4" PVC couplings, on end, as bases for another layer of "egg crate" on which all of the sump equipment set. The sump was a Rubbermaid container, 85% of the surface area of the tank it supported (and the one still running is 100%). (Please note that a 4" PVC coupling is approximately 5" long so there is about an inch between the rack and the surface of the sand itself.)

Upon draining the tank and sump, I was pleasantly surprised to find that the DSB was not compacted, darkened or odiferous. The "silt", to which mr. wilson refers, was abundant and I suspect a result of some chemical breakdown of the bed itself, much like a Ca reactor.

I do notice, over time, that my beds' volume diminishes. The evidence of this is that the PVC couplings become exposed. As a result of this, I do "top-off" the DSBs, adding new media like I do dirt around a tree; slowly and shallowly so as to allow the life in the bed to not be buried too deeply and die as a result.

Visual of inspection of the smaller tank's sump, set up in a very similar manner but using an actual glass tank rather than a plastic tub, allows me to see that only the top 1" - 1.5" of the sand is actively colonized. 2.5" - 3" remain very much like it looked when I set it up. I cannot see the plenum, as I have about an inch of sand between the glass and the plenum's structure.

I have never had many problems with cyano outbreaks, HA or nitrates in either tank, although they are lit for the benefit of different creatures. The few problems I have had have always been after a prolonged trip and I suspect stemmed from overfeeding by my "pet nanny".

An interesting note for mr. wilson: the eggcrate "rack" layer is covered in sponges and tubeworms.

 

[mr.wilson]

<a href=showthread.php?s=&postid=10342236#post10342236 target=_blank>Originally posted</a> by token
An interesting note for mr. wilson: the eggcrate "rack" layer is covered in sponges and tubeworms.

I've often wondered how much detritus/heavy metals tube worms collect along with the calcium carbonate they use to build their casings. It would be interesting to see if the worm casings could be periodically harvested to export heavy metals and excess nutrients. I'm referring to larger tube/fan worms of course. The tiny duster clusters and hard tube worms in your egg-crate are a little small for the task.

They appear to work harder (faster) to replace the casing when they are lost or damaged in shipping or movement within the tank. I'm not proposing that they can replace mechanical filters for removal of POC (particulate organic carbon), but they may have a value in the assimilation of DOC (dissolved organic carbon).

As a gardener, I'm sure you are well aware of the high nutrient content of worm casings.
Worm casings are a highly sought after fertilizer, which is the last thing we need in a reef tank. If one were to set-up an egg-crate tray with 50 or so large (feather duster) tube worms in the sump, a critical mass may be reached.

Many hobbyists have experimented with scallop colonies in their sumps as a means of water polishing. They are great filter feeders, but appear to be susceptible to bacterial algae (cyanobacteria), and require concentrated feeding for long term success. Once you have to feed a "bio-filter", it fails to be a viable assimilator, dissimilator or exporter and becomes just one more mouth to feed.

Tube/fan (serpulidae) worms are non-photosynthetic, and fair well in nutrient-poor environments, so they are well adapted to life in a sump. They are capable of polishing the water through filter feeding, and they can act as a means for exporting excess nutrients in the form of their protective casing (tube).

But of course this is all conjecture, as is most of the technology and methodology we use in this great hobby.

 

[thriceanangel]

Wilson,
I believe that you are referring to worm castings (poop) that is a valuable fertilizer. There are farms that convert cow manure to worm castings via the good ol earth worm, which of course has no case as it's an oligochaetes annelid. Worm casings are totally different and are produced by polychaetes worm in the Serpulidae family. I don't know how useful the carbon removal would be in this day and age where people are dosing it...

 

[mr.wilson]

Same casings, different worm.

 

[thriceanangel]

?

 

[mr.wilson]

Terrestrial and aquatic "worm castings" are also referred to as "worm casings" or "vermicast".

Earth worms have evolved from their tube worm cousins in the sea. They are both in the phylum annelida.

The same process performed by earth worms on land is carried out by serpulid worms in the sea. Earth worm casings and serpulid worm casings are both rich in nutrients (heavy metals).

If bioassay confirms that the soft tubes are high in heavy metals, then they are worth further study as a means of export. If the tube is comprised mostly of calcium carbonate, with only a marginal quantity of heavy metal content, then they would only be valuable as assimilators (breaking down nitrogenous waste).