Plenums and the wasting "option"

[ddoering]

Hi All,

Just a little fun for the particle sizes for substrate, since some of you are looking at layering etc, and others want to support gobies etc.
From:
http://www.wetwebmedia.com/deepsandbeds.htm

From this link it states that sand sifting animals do best with
.2mm to 1.0mm substrate

This is the oolitic sugar sand size, which is good for denitrification
with shallower depths etc.

From:
http://www.rshimek.com/reef/sediment.htm

Dr. Ron states a good compromise grain size for sand beds is .125 mm
or 1/8th mm which is less than the size range for oolitic sand, and
refers to this as mud and not sand for the DSB approach of lots
of worms etc. The small fauna in the sand likes the smaller grains.

Substrate size should be determined by the lifeforms you are trying to
promote, if you want sand sifting gobies, go with oolitic or fine sand.
If you are trying to promote more of a mud filter with lots of worms and
pods and microcrustaceans etc, maybe go with the DSB of good old southdown.

From:
http://www.reefkeeping.com/issues/20...hcs3/index.php

Sand sifting gobies may bite down 1.2 inches into the sand while
sifting for feeding, so I would guess that your top layer should
be a fine sand substrate at least 1.5 inches or deeper.

It also states that these guys are going to clean out your living
sandbed, so a deep sandbed and sand sifting gobies is probably
a bad idea without having a huge aquarium with tons of sand
for these guys to not decimate the sandbed fauna.

In nature they forage over a square meter, and may have multiple
burrows and actually require up to 5000 square feet of forage
to support a pair of gobies.

They will quickly deplete a sandbed of fauna, leaving only
bacteria.


For NNR with a sandbed, this is bad news, since the main way
that a sandbed consumes nitrogenous wastes is with bacteria,
and the way that bacteria consume so much waste and convert
it is by reproduction. If the sandbed gets to the point where
there is nothing eating the bacteria/microalgae in the sand,
the sandbed will not be able support a growing population
of bacteria, so will not process as much waste in the tank
leading to nitrate, nitrite, ammonia in your display tank
water.

If your main goal is keeping sand sifting gobies in the display
tank, I think you might want to keep your DSB for processing
wastes separate from the main display, and put just enough
sand in the main display for aesthetics and to support the gobies
(maybe 2 inches), and not worry about supporting any fauna in the
main display, instead leaving this to a DSB in fuge/sump/separate
tank. You'd have to supplement the gobies food and get them
eating prepared foods instead of what they just scavenge from
the sandbed. And anything that does manage to survive in the
display tank sandbed is just extra and snacks for the gobies.

Dr. Ron's article above also states that most clumping in sandbeds
is not the result of calcium precipitates, but from bacterial
secretions.
***
Some bacteria also secrete a exterior covering called a glycocalyx.
These are made of a hard sugar-like material similar in consistency
to rock candy. Rapid bacterial growth may produce enough of this
material to glue sediments together. These sediment lumps may be
glued so tightly together that hammering is needed to break them
apart. In much reef literature, these lumps are said to be caused by
calcium carbonate or calcium phosphate precipitation. Such mineral
precipitation is rare; if a small sediment lump is placed in a weak
solution of household chlorine bleach, it breaks down to the
component sediment grains in a short time. If the lumps were formed
from the calcium salts, they would not dissociate in the bleach.
***
Dr. Ron's solution to prevent clumping from fouling the sandbed
is to have a large diversity of worms, pods, etc that eat the
bacteria from off the sand surfaces. This also allows for the
bacteria populations to continue to reproduce as free space
is made in the sandbed, which maintains the sandbeds ability to
process nitrogenous wastes.

Just some reading I did instead of working today

Time for me to put a few hours in of real work while it is
raining and give people time to post replies.

Cheers,
Doug

["Umm, fish?"]

salty joe: Sounds like it to me, as long as you are getting the phos out before it migrates back up into the water column.

Doug--The problem, as you point out, isn't the phos that stays in the water column long enough to get whisked away to a fuge or protein skimmer. So, wasting isn't the only technique we are (or at least, I am) trying. We are also doing what we can to keep detrius suspended long enough to get it out of the display tanks. The challenge is doing this while maintaining a sand bed.

You say, "The P would leach back into the water column if the anaerobic layer approached the surface of the substrate." I think that's one of the reasons barryhc is so gung ho on stretching the aerobic layer down. But, I can't truly speak for him, of course.

Anyway, interesting ideas. Keep 'em coming.

[barryhc]

Originally posted by ddoering
Hi Barry,

Ok, just to keep me on the same page.

Aerobic: requires oxygen
NH3 to NO2-
Ammonia to Nitrite

NO2- to NO3-
Nitrite to Nitrate

Anaerobic: requires no oxygen
NO3- to N2
Nitrate to Nitrogen gas

ooPS! Wait a minute, the most predominate Nitrate processing occurs by way of "Faculative Bacteria", which are "non-obligate Anaerobes", and which primarily function in a very thin layer of "low oxygen" in the substrate and elsewhere. I am not particularly interested in "stretching" the Aerobic layer of substrate, but it is going to happen, and "so be it". However, the "low-oxygen" zone just above the Anaerobic, is generally "very thin" by most scientific studies and dissertations on the subject, and this is what limits the amount of nitrate processing that a sand bed can accomodate.

It is this "low oxygen" zone that I am most interested in "stretching", to the benifit, of course of the Faculative bacteria, and their Nitrate processing capabilities.

Below this is the Anaerobic zone which is more likely to produce hydrogen sulfide, which we don't want, which zone must become thinner, if of course, if we have "stretched" the Aerobic and "low oxygen" zones above it.

It is the production of Hydrogen Sulfide in the Anaerobic zone of DSB's that has really been the worst condition that has caused severe failures, and lessened their popularity to a considerable degree. The "DSB crash"! This is the first and foremost negative of DSB's that I am looking to eliminate. Nitrates and Phosphate can be dealt with in various ways "if need be", but not Hydrogen Sulfide. Let us be sure to reduce it's formation, and "waste the rest"!

This also makes me wonder if you are just shooting yourself in the foot by drawing oxygenated water down into a deep sandbed in order to extend the aerobic area.

You have not read enough of this thread, Please don't take this the wrong way, I particularly appreciate your input, but I have responded to this very point over and over.

(Now this may be a reason FOR using a silica based substrate instead of aragonite/southdown type sand since the P wouldn't bind to it since it isn't calcium carbonate).

I have already made this point also, but at least you are bringing it up, and silica also does not have much P in it, and does not "melt" at low pH, so the substrate does not "reduce", and cause clogging.

From my first post, I would test the time it takes to make your standard sized draw and see if it is increasing the longer the system is running, as this would be a way to judge compaction or restriction of flow in the sandbed.
.
From my second post, if people who have set up a system with the plenum space can visually inspect the bottom of their tank glass to see if small particles are accumulating in the bottom of the tank that would help to understand how effective layering is at restricting particle migration, or if bacterial processes are resulting in accumulation of solids in the plenum.
.
From this post, if you are testing the plenum or wasted water to measure levels of phosphate being removed, make sure to measure temp and pH of the wasted water to compare to the P level in the water column above the substrate to see if there is a true accumulation in the bed, or simply a higher level of measurable P due to lower pH and the phosphate not binding to the substrate as well at that pH.

These are valid points, but with frequent wasting ( like "daily" ), If there is P in the effluent, it is being exported, and if it is not at higher levels than in the water column, then are we going to complain about that?

Remember, for me anyway, If the sand dwelling critters like it, and it doesn't "crash", then I am happy!

> barryhc

[ddoering]

Hi Joe,

I'm not saying that you won't be exporting some phosphate by wasting from below the sandbed, but what I want people to be clear on when testing is that they don't draw the wrong conclusions from misleading numbers.

Since the pH from plenum waste should be lower than the tank, I would expect tests to show higher value of P in solution than testing the water column.

But this wouldn't be proof that P is accumulating in the lower areas of a DSB. Some people might draw the conclusion that since the plenum waste tested higher for detectable phosphate levels, that was an indication that P is accumulating in the lower levels of the DSB.

A higher P value on a test with lower pH may actually represent an equilibrium with the P in solution in the water column, and not demonstrate P accumulating in a nutrient "sink" in DSB without wasting.

Testing over time where the P value in the water column stays the same but P in plenum wasting increasing (making sure to correct for pH differences in the waste drawn off) WOULD demonstrate P accumulating in the DSB and go towards proving the DSB is a nutrient sink theory.

Dr. Ron's theory on how the DSB works doesn't state the DSB is a bottomless hole where P can just continue to build up, but depends on bacteria and animals in the sandbed providing different pathways to free up P to be exported by other means from the water column. This would be by skimming to get the organic molecules/proteins, or by growing macroalgae to absorb orthophosphate (which would be the P in solution) coming up out of the anaerobic area of a sandbed. The sandbed would process P by binding it within organic molecules by animals reproducing and producing larval forms that go back into the water column and are consumed by corals and fish and incorporated in their biomass, or the larvae getting skimmed out, or by putting P into solution as orthophosphate that would then be processed out by macroalgae in a fuge etc or microalgae consumed by the sandbed fauna/tank cleaners.

Since calcium carbonate particles will have phosphate absorbed to their surface, eventually all the phosphate absorbtion power of a given amount of substrate will be consumed. How long this takes with a constant P concentration in the water column of the tank before the substrate is saturated is unknown. This may be seen as the initial usefulness of the DSB in being able to prevent high phosphate levels. Once the substrate is saturated, the DSB then has to process phosphate by lifeforms utilizing it or by forcing it into a soluble form to be stripped from the water column instead of acting as a chemical scrubber.

In the setup being proposed here, layering of different grain sizes is supposed to prevent particle migration. If particles of substrate that are saturated on their surface with phosphates are not migrating down into the anaerobic area, then I have doubts that plenum wasting will remove any more phosphates than taking the same amount of water from the water column.

My reasoning is this. If higher pH causes phosphate to bind with substrate surfaces for calcium carbonate, the water that replaces the draw off water by drawing water down into the substrate will have already been stripped of excess phosphate by precipitating out.

Then the pH drops, so more phosphate could be in solution, but there isn't any on the substrate at this level.

What you would need to do to scrub the phosphate off the substrate would be to migrate the substrate from aerobic to anaerobic areas (read as lower pH) so that any encrusting phosphate would then go into solution, and then drain this water
off, and then put this now cleaned substrate back to the aerobic layer (read as higher pH) so that it can absorb more phosphate from the water column.

If only the water is moving, and you are drawing it from high pH to low pH, then the water coming into the plenum or lower area of the sandbed would have less dissolved phosphate than the water would allow, but since the substrate at this depth was not subjected to the higher amounts being deposited, the allowable
amount would not be utilized, so you would end up only drawing off as much phosphate as you would have by drawing off an equivalent amount of water from the water column. This is why I want to see the levels of phosphate in the plenum waste as compared to what is in the water column. The only way
I can think to cycle the P from off of substrate would involve turnover of the substrate, which is something that Dr. Ron says happens in an undisturbed sandbed where the critters movements migrate particles like earthworms in a garden.

So I do believe there is a sink that the substrate will leach back into the system, but I don't believe this is due to a DSB vs SSB etc. The only difference would be that the DSB would have more surface area for absorbtion so would take longer before people noticed a P problem if they wait for algae outbreaks to be their initial sign of a problem. With a larger amount of stored P due to surface area for absorbtion, it would take longer for corrections to input/output of P to consume stored up P, so the battle with
undesired algae would be longer before it was resolved.

Basically all the above is just me thinking out loud, and while I agree that you would be able to export phosphate from the bottom of the tank by plenum wasting, the question is if this is more efficient than just doing a water change from the water column for the same volume of water. Is the same amount of P being removed in each case? Maybe another thing for people
to test.

The reasoning behind wasting from the bottom of a sandbed is that this is supposed to be a concentrated area of waste that if left untouched will accumulate and eventually result in a nuked tank. If there is no accumulation happening, then plenum wasting is not necessary, and it would be more efficient to skim better or set up a macro algae fuge to consume P from the water column.

Anyway, this reply was longer than I thought it would be, but just my random thoughts.

Cheers,
Doug

[barryhc]

Well Doug, we are "passing replies" here again, we're both typing at the same time and the wrong one posts first, making it look like we are ignoring each other, hilarious!

The layering scheme I just recently posted was not meant so much for you, as it was for Steve, and everyone in general, but you need to read it carefully, very carefully.

Originally posted by ddoering
Hi All,

Just a little fun for the particle sizes for substrate, since some of you are looking at layering etc, and others want to support gobies etc.
From:
http://www.wetwebmedia.com/deepsandbeds.htm

From this link it states that sand sifting animals do best with
.2mm to 1.0mm substrate

This is the oolitic sugar sand size, which is good for denitrification
with shallower depths etc.

Very good, It also states that 1-2mm is "borderline", which makes my reccomended .7-1.7mm just about perfect heh?

From:
http://www.reefkeeping.com/issues/20...hcs3/index.php

Sand sifting gobies may bite down 1.2 inches into the sand while
sifting for feeding, so I would guess that your top layer should
be a fine sand substrate at least 1.5 inches or deeper.

So I guess the previously described Layers # 1 and #2 are still about perfect for this, being better than borderline for gobies, and still able to "reject detritus" and avoid "sand storms", even if we used .7-1.7mm for the entire depth of layers 1 and 2, of 3" total depth.

It also states that these guys are going to clean out your living
sandbed, so a deep sandbed and sand sifting gobies is probably
a bad idea without having a huge aquarium with tons of sand
for these guys to not decimate the sandbed fauna.

In nature they forage over a square meter, and may have multiple
burrows and actually require up to 5000 square feet of forage
to support a pair of gobies.

And so, you are stating here that people with less than 5000 sq. ft. of sand bed, do not successfully keep gobies? I suppose that you believe that "dendros" cannot be kept either.

They will quickly deplete a sandbed of fauna, leaving only
bacteria.[/B]

I continue to insist that the display substrate, is not the place to keep your "food factory". Refugium's are much better for this, regardless of how much Nitrate and P that they do or do not "process".

For NNR with a sandbed, this is bad news, since the main way
that a sandbed consumes nitrogenous wastes is with bacteria,
and the way that bacteria consume so much waste and convert
it is by reproduction. If the sandbed gets to the point where
there is nothing eating the bacteria/microalgae in the sand,
the sandbed will not be able support a growing population
of bacteria, so will not process as much waste in the tank
leading to nitrate, nitrite, ammonia in your display tank
water.

This is not a sand bed, this is a "Wasting Plenum" version of substrate. It is just about time for you to start reading this thread, and respond to the answers that have already been given to these concerns.

If your main goal is keeping sand sifting gobies in the display
tank, I think you might want to keep your DSB for processing
wastes separate from the main display, and put just enough
sand in the main display for aesthetics and to support the gobies
(maybe 2 inches), and not worry about supporting any fauna in the
main display, instead leaving this to a DSB in fuge/sump/separate
tank. You'd have to supplement the gobies food and get them
eating prepared foods instead of what they just scavenge from
the sandbed. And anything that does manage to survive in the
display tank sandbed is just extra and snacks for the gobies.

This is what I just got done explaining about 2 or 3 times in the last page of posts, not including the 2"of substrate, which has been shown to be rather detrimrntal in general, over the past 10 years.

Dr. Ron's article above also states that most clumping in sandbeds
is not the result of calcium precipitates, but from bacterial
secretions.[/B]

Dr. Ron has not done any experimentation, or even any consideration of Frequently Wasted Plenum Substrates.

You will note that this post seems a bit reactionary, and for good reason. I don't often operate this way, but if you don't start responding to the explanations that are given, instead of sounding like a BB "parrot" I will lose interest.

> barryhc

[barryhc]

Again and again and again, this thread is for those who insist upon having a substrate, and has become primarily for those who require animals that they prefer, which require a substrate.

Happy animals, and NO CRASH is the PRIMARY objective of the "Wasting Plenum". I am confident that Nitrate and P processing are also going to be better than in a standard DSB.

SaltyJoe already hit the nail on the head with "Job accomplished", and so did you with "silica sand" or other, which has already been covered.

Doug, the "devil's advocate" scenario has played itself out, it is time to get on board with solutions VS problems.

It is going to take a while to prove what is and isn't working with this system. For your current concern, please visit "Biological Phophorous Removal" and "waste treatment"studies", a wealth of information to absorb in these subjects.

Stay with us, It is going to work! >barryhc

[sradmin]

Barry,

Thanks for your patience in explaining your proposed layering. I have one other favor to ask of you... I've been trying to UTSE for a couple of days now, but as usual, it's down. Even tried early monday afternoon- still down. Everyone must be on RC instead of working. Anyway, I'm looking for any RC links having to do with biological phosphorous removal- do you have any you could provide a link to?

[barryhc]

Steve, try this. It is getting to be a couple of months old now, but it is terribly interesting reading just the same. Javajaws may hqave given up on vodka dosing, or is otherwise disposed, but the vodka dosing isn't the good part anyway necessarily, it is the waste water management. Back up to the first page.

http://archive.reefcentral.com/forum...6&goto=newpost


> barryhc

[ddoering]

Hi Barry,

Missed your post in passing.

I read the whole thread before my first posting, I just differ in opinion on some of your conclusions.

Until you have tested the theory, don't assume your presumptions
as fact. I am bringing up things that I would test for to see if your assumptions are being born out in a real world test.

Also, as you have repeatedly stated throughout this thread, not
everybody is setting up exactly the same type of system, and
the point in people trying different things is to hopefully find
a better way of doing things, or at least giving people ideas to
try to see if they can find a solution to a specific environment
that they are trying to set up.

As you have said, one of these ways may be better than the
current ronco faction of dumping in a bunch of substrate to
create a DSB and "set it and forget it" approach.

Also, please do not lump me in with the BB group, I have never
advocated a bare bottom system, my opinion of BB tanks is they
are ugly. I like substrate on the bottom of the tank, and I
think the more diverse creatures you can get in your tank the
better because half of the interesting things to look at are
the sandbed critters and weird stuff, crabs, snails, worms.

I also do not like the wall of coral setups, where I think
some are pretty to look at, my ideal setup would be more of
a mini functioning ecosystem than just a display of corals maintained in as sterile an environment as can be provided by extreme circulation, over skimming, and uv or ozone sterilization.
I like planted tanks, and ones with various macro algaes
in the display, my main tank will be more of a large
refugium that happens to have some corals than the other way around.

...

Now, not to be a devil's advocate, but I don't think you can
"stretch" the interface layer between where aerobic respiration
will occur, and where anaerobic respiration will predominate. The
faculative anaerobic bacteria preferentially use oxygen, so if oxygen is available, they will not be processing nitrate into N2 and NO gases and will consume oxygen.

You may be able to stretch the aerobic portion of the sandbed, and shrink the anaerobic layer, but I think the interface is going to remain about the same thickness. This is just my gut feeling, so testing to show I am wrong would be great.

One concern of draining from the bottom and getting rid of the
anaerobic area of the tank would be that you are creating a
nitrate/nitrite factory out of the sandbed. If the interface
layer that processes nitrate does not stretch, wouldn't this
result in a system similar to trying to do your filtration with
biowheels and bioballs? A large aerobic processing that is great
at reducing ammonia to nitrite and nitrate, but then gets bottlenecked in reducing the nitrate to nitrogen gas.


Also, my understanding is that a good portion of the diet of sandbed critters is anaerobic bacteria:
http://www.reefs.org/cgi-bin/ultimat...&f=28&t=000027
***
Having said that, I explained the activity of the meiofauna (animals that live between sand grains in a sandbed) in the FAMA articles as well. The punchline is essentially that these animals are quite tolerant of high sulfide concentrations and, in fact, frequently burrow well into the sulfide reduction zones, which causes slow relase of sulfide as suggested by Randy. These reduction products are typically oxidized once they penetrate the aerobic layers of the sandbed if their movement is slow, and are also often consumed by animals in those layers. In fact, the reason that these animals burrow into the sulfide zones is for feeding -- they eat the reduced compunds present in the anoxic regions of the sandbed. In fact, the meiofauna provide an important and major pathway for nutrients to re-enter the aerobic zone of the sandbed above the sulfide reduction zones (as I mentioned above). This explains why people often observe animals or animal tracks/burrows in anoxic regions of their sandbeds. For example, anaerobic sulfur bacteria may account for nearly 1/3 of the diet of ciliates, and grazing rates by infauna averaged something on the order of 3% of the total bacteria and 1% of the total diatoms in the sediments per hour in highly productive regions of natural estuaries.

The diet of meiofauna examined consisted primarily of diatoms, flagellates, sulfur bacteria and “other� bacteria (including cyanobacteria and chemoautotrophic bacteria), which together accounted for over 90% of the diet, the relative contribution of each depending on the species. In all cases however, when researchers examined the diet of specific taxa of sand infauna, anaerobic bacteria were important enough to be named specifically as one of the main diet items rather than being lumped into the "other" category.
***

The above implies that the anaerobic area is very much needed to support the sandbed critters, maybe not necessarily the specific critters you are looking at maintaining (sand sifting
gobies), but the little ones that graze the bacteria and
keep the biological filtration able to continue to process
ammonia nitrate nitrite.

Also, from the reading I have done, it seems pretty much an accepted fact that the way that a sandbed performs the job of NNR is by providing a large surface area for the bacteria to colonize. The continued success of the sandbed to maintain a useful level of NNR capability is room for the bacterial populations to expand. If there is not something in the system that is keeping the bacterial population in check by consuming it (read this as
sandbed infauna), the sandbed will max out relatively quick.

My statement about the gobies and the amount of space they
require in nature for foraging is to give you an idea that they
can easily overgraze your sandbed fauna. This is not only of
concern for producing food for your corals by these populations
breeding, which I consider a secondary benefit and not the main
concern, but it will prevent the sandbed fauna from keeping the
bacterial populations pruned, which will reduce the ability of
the sandbed to act as an ammonia/nitrite/nitrate consumer and
will lower the biological filtration in your setup.

Possible suggestions for a person who MUST have a sand sifting
goby in their display:

1) make the biological filtration remote from the display by having
your deep sand bed in a fuge or sump or remote tank.

*NOTE* this does not mean that you can't also have substrate in your
display tank for the goby to burrow in, and for other aesthetic
reasons, I just think that you can't count on the display substrate
to have the same NNR processing capability with a goby in there
cleaning out all the little sandbed critters that eat bacteria
and allow the bacterial populations to continue to reproduce
(which is where they consume the ammonia/nitrate/nitrite and even phosphorous)

2) Since a sand sifting goby is going to be stripping the small
crustaceans and worms etc from the sandbed (and without a huge tank this will be done faster than the sandbed critters can repopulate) add another creature to the display that would do the same job as the microcrustaceans etc.
What other creatures consume sandbed bacteria that the goby will not consume?
Only thing that comes to my mind is cucumbers that ingest great
deals of sand and strip the bacteria before excreting the substrate.

Now you may have to also add some extra algal grazers to keep up with microalgae, so maybe you need more snails and hermits than somebody with a DSB with lots of sand critters and worms. Also if there are any detrivores you can add that the goby won't eat that would help.

Both 1 and 2 don't require a typical DSB depth in the main display,
so you would be able to use only enough substrate for the goby to be happy, which I guess is a couple of inches, and this would then not be something that would result in an anaerobic zone in your main display, and you would not need to set up the wasting plenum to prevent H2S buildup. Especially with the cucumbers mowing through it and the goby sifting and digging around.

Now where a wasting plenum would be useful, would be in tanks that do maintain an anaerobic zone. This would be useful if you could demonstrate that DSBs do accumulate detritus/toxins deep in the bed that the wasting plenum could be used to remove. This would extend the life of a DSB or at least improve on water quality issues when utilizing a deep substrate.

Or if you can demonstrate that the sand bed concentrates P for
removal then this would make drawing from the bottom of the bed
more useful than just a normal water change and skimming/macro algae.

Basically I think the first step is going to be building and testing
a tank with the plenum wasting, and accurately testing the waste
water to see if it is actually accomplishing what you want. Since
no two tanks are going to be the same, standardizing what things
should be tested in different environments should help in comparing which system is more effective.

Since this will probably take years to show any benefit over a
DSB system (since those take years to nuke themselves if ever) you need something you can test along the way to take as a benchmark of the progress you are making, which is why I suggested keeping track of flow rates to see if the bed is compacting from sucking water down through it, as well as monitoring the plenum for any accumulation of solids/silt.

If I can think of a possible solution to a problem, I'll post it
as it comes to me, but my brain works more towards finding problems than solutions. Once the possible problems are identified you can look for solutions, but you can't start with the solution and hope it addresses all things.

One thing I haven't found in reading is what is the process of exporting sulfur compounds in non DSB systems? If the concern with DSB is hydrogen sulfide gas accumulating until it nukes the tank, is there a sulfur cycle like the nitrogen cycle?

Cheers,
Doug

[barryhc]

Doug, you write better than you read. 95% of your last post is what I have been stating for 3 mos.. and most since after you posted in this thread. You have missed my continual insistence, that the water will be drawn at whatever rate maintains the bacteria the best, including an albeit "somewhat thinner" anaerobic zone. Neither gobies or anything else is going to disturb the meiofauna in the 1 1/2" of oolitic sand that is under the Critter screen.

You also have "microfauna"and "macrofauna" . Since gobies "bite into the sand as much as 1.2" deep, that is going to keep them 1.8" away from the oolitic sand where the "low oxygen" zone should likely begin and harbor non-obligate faculative anaerobes.

If the distance from the oxygen saturated surface to the beginning of anoxic sediment is made farther ( stretched by high frequency wasting ), which it will be, then the low oxygen zone of pore water will become thicker. If nutrients in the pore water are drawn into the sandbed by "flow" as opposed to diffusion, then there will be more food for the faculative bacteria to utilize. The non-obligate Anaerobes are not going to crawl up into the substrate to get more oxygen, and then neglect the low oxygen layer in the substrate.

One concern of draining from the bottom and getting rid of the
anaerobic area of the tank would be that you are creating a
nitrate/nitrite factory out of the sandbed. If the interface
layer that processes nitrate does not stretch, wouldn't this
result in a system similar to trying to do your filtration with
biowheels and bioballs?

You cannot have read and understood my posts, and then MEANINGFULLY offer this response.

There is plenty of room in the layering model that I have proposed, for both gobies, and "most types of fauna". Not enough fauna to feed the gobies, but plenty to maintain the substrate. Food factories for fish and invertebrates belong in refugiums where they can foster themselves without predation.

Now where a wasting plenum would be useful, would be in tanks that do maintain an anaerobic zone. This would be useful if you could demonstrate that DSBs do accumulate detritus/toxins deep in the bed that the wasting plenum could be used to remove. This would extend the life of a DSB or at least improve on water quality issues when utilizing a deep substrate.

I think your glasses or some other obstruction is filtering out all shades of gray, and allowing only black or white to make it thru.

Do a search on "SRB" Sulfate Reducing Bacteria, and then try that Biological Phosphate Removal thread that I just posted for Steve. You will find this quite enlightening.

I must apologize for the reference to BB, I admit that was a really low blow, however, you need to really brush-up on your reading and comprehension skills, there seems to be some empty space between the in and out holes.

It is GRAY matter that belongs in there. Keep practicing.

> barryhc

[ddoering]

Well Barry,

It appears that you take any differing opinion or theory as a lack of ability to understand.

Please point me back to the posting where you provide your documented results from having built and test this system successfully.

Please include the detailed steps you took to measure the contents of the plenum waste water, the oxygen gradient in the substrate, what was measured, and what controls were in place so that others can repeat your experiment and validate your results.

Oh... wait... have you implemented this system yet?

What makes you think that the low oxygen layer where most nitrate is converted to N2 is done WILL be stretched by pulling water into the sandbed? Simply pulling oxygen rich water into the substrate does not guarantee that the interface area will be thicker.
I would think this would just push the interface layer lower into the substrate, but that it would still remain a very thin layer, the reason being is that the reaction occurs at the interface area between aerobic and anaerobic conditions.

Also, lets not mix terms here, as you were so adamant about that in previous postings by others.

Anoxic is an adjective that means without oxygen. For example, anoxic ground water is ground water that contains no dissolved oxygen.

Now some places use "anoxic" interchangeably with "anaerobic", and some places try to distinguish "anoxic" and "anaerobic" stating that "anoxic" is a region of very low oxygen concentrations, but not totally without oxygen.

There are only two processes though, aerobic, and anaerobic. At the interface between these two areas is going to be a thin layer where Faculative Anaerobic Bacteria can predominate since they can survive both conditions.

Above the interface layer, FAB is outcompeted by the aerobic bacteria, and below the interface layer FAB dies off after consuming the available nitrate, so it is replaced and out competed by true anaerobes that utilize nitrate AND other compounds that are available.

The problem I see with the stretching theory of the interface layer of low oxygen is that it will be quickly converted to anaerobic on the lower portion, or will constantly being flushed with new oxygen source on the upper portion, so never reach the steady state where oxygen coming in equals the oxygen being consumed.
The FAB establish themselves in the interface area that is a steady state condition where oxygen in = oxygen consumed. I don't think you will be able to maintain this over any greater thickness with any type of stability. Instead I see the interface jumping up and down when you waste water from the bottom which results
in the low oxygen zone fluctuating. Since the zone would be fluctuating up and down, will the FAB ever be able to establish a dominant population over the full aerobes or full anaerobes to provide the greater nitrate processing you are looking for?

If you did a steady state constant flush from the plenum, I think this would just cause the interface layer to occur lower in the substrate, and not affect the thickness of the interface layer.

The only number I came up with to describe what constitutes the low oxygen concentration was a statment saying it would contain about 1 part per million (ppm) oxygen.

Set up your test system, and devise a way to measure the oxygen concentration at varying depths in the sandbed, and if you can maintain 1 ppm of oxygen over a large layer in the sandbed great, that gives you a starting point.

I would suggest that testing your oxygen gradient be done immediately prior to your wasting water from the plenum, and immediately after.
You would also need to have a constant oxygen level in the column of water over the substrate for testing purposes, otherwise your measurements will also fluctuate due to the incoming water having varying oxygen levels.
You would also need to have a constant level of ammonia/nitrate/nitrite/detritus in the water column above the substrate for testing, or your measurements will also fluctuate due to the differences in food sources which will fuel different levels of oxygen consumption in the sandbed.
You would also need to have constant pH levels, and other water parameters in the water column to prevent this from causing fluctuations in your measurements.

You need the oxygen gradient from both ends of the spectrum to try and tweak it so that a greater thickness of the bed stays in the range of 1 part per million oxygen.

To complicate your testing, you do not have a uniform bed of substrate, and the oxygen gradient will be affected at these interfaces between substrate sizes where water volume will be different due to the displacement of different grain sizes, and established bacterial colonies will differ in population and amount of what they consume due to the differences in surface areas available for the bacteria to populate.

You would also need to waste the same amount of water each time (an easy way to control this was the U tube idea).

How you control all the other variables is going to be up to you to figure out.

Of course you don't need to do controlled testing of your theories, you can just set the tank up and play with it as you go along and see how it works out for you.

All of your results though would be anecdotal unless others can repeat in similar setups your results.
If you do just set it up and go with it, keep accurate measurements and test consistently so that you may be able to draw reasonable conclusions.

Until you have results, or at least controlled experiments and some measurements to back your theories, attacking people who question your assumptions or pose possible problems with your assumptions results in an end to dialogue.
This is a discussion board, it is intended to allow the free flow of ideas back and forth.
If your mind is already set on how you are going to do everything, and there is no room for people to propose possible problems with what you suggest, why are you even on this message board?
As you have all the answers already, and anybody disagreeing with you is somebody who can't read, or is unable to comprehend your brilliant master plan, I'll just post these comments for the other people following the thread:
.
According to Barry:
***
There is plenty of room in the layering model that I have proposed, for both gobies, and "most types of fauna". Not enough fauna to feed the gobies, but plenty to maintain the substrate. Food factories for fish and invertebrates belong in refugiums where they can foster themselves without predation.
***
If there is not enough fauna to feed the gobies, how can there be enough to maintain the substrate?
The gobies are not going to stop feeding at a certain point to leave the fauna present to maintain the sandbed.
Before I would buy into this layering scheme I'd determine what "most types of fauna" are, and how it is judged that what remains after a goby's foraging is enough to maintain the substrate.

***
You have missed my continual insistence, that the water will be drawn at whatever rate maintains the bacteria the best, including an albeit "somewhat thinner" anaerobic zone. Neither gobies or anything else is going to disturb the meiofauna in the 1 1/2" of oolitic sand that is under the Critter screen.
***
Ok, so because you insist it, it will be so. Just wave a magic wand and start with an assumption and work your way backwards to the beginning.
If things happen just because you insist they will, then just insist that your water parameters remain perfect.

Please answer HOW YOU WILL DETERMINE THE RATE AT WHICH TO DRAW WATER?
A blanket statement of whatever rate maintains the bacteria the best is meaningless wishful thinking.
First you need to determine which bacteria you are trying to maintain.
Second you need to define what you mean by maintain? If by maintain you mean have a stable population of bacteria that is being consumed and replaced by reproduction, this is different than establishing and maintaining a population without predation.
Third you need to determine the requirements to maintain the bacteria.
Fourth you need to postulate how you will provide this environment.
Fifth you need to perform testing to see if your theories hold true, so you need to determine what you can test for that will help to confirm your theory or refute it.

Before tackling any problem, you need to define the problem clearly. In the months that you have been posting this thread, you have never really made a clear statement on what you are trying to accomplish that is more detailed than happy critters and no crash.

Since this is a very generic description a lot of time has been wasted in getting you to refine your criteria.

This was then refined to be:

1) wanting to maintain creatures that require substrate in the display tank
2) no crash

#1 was then refined to sand sifting gobies and other critters that require a deeper bed
Since crashing of an aquarium can be caused by any number of bad husbandry techniques, #2 had to be further clarified by trying to strangle out of you what you think causes tanks with deep substrate to crash.

At one point in the thread, it was stuff accumulating in the bed like P, at one point it is possibly heavy metals, and most recently your accepted cause of DSB tanks crashing is H2S gas nuking the tank.
In order to know if you are being successful in your methods, you need to demonstrate that the problem you are trying to resolve exists in the first place to know if your measures are having an affect on preventing it.
This is why I brought up testing the waste water from the plenum to see if you are actually experiencing any of the problems you are trying to correct.

If you don't see any problem, the easiest solution is to just do a DSB.

Now you don't want a DSB, fine, you want a wasting plenum, great, you propose a layered scheme for substrate to prevent particle migration into where you draw the waste from so that you won't have clogging, and a pipe matrix with holes spaced out with diameter differences to provide a pressure drop
and get an even draw from beneath the sandbed. This is about the only thing that is in this thread that shows a step in the right direction. I'm not saying the layered substrate will be successful, but at least you have identified a problem and proposed a solution.

The problem was getting an even draw from beneath the sandbed without clogging, the solution was the layered substrate to prevent particle migration.
Ok, did you test your solution?

It is not useful to throw a bunch of assumptions together into a complex system, like a reef aquarium, and then draw conclusions on your results.
Your layered substrate may stop particle migration at certain flow rates, but if the flow rates are large enough you could end up with channelling or a fluidized bed that allows larger particles to migrate through.
This is why I suggested a simple means of testing if your flow is being restricted so you can rule out or confirm if flow is changing which would be a source of error in your results.

Identifying sources of error is useful for the next generation so people can try things to improve on to make it a better system in the next iteration.

On to the next assumption without proof:
***
Since gobies "bite into the sand as much as 1.2" deep, that is going to keep them 1.8" away from the oolitic sand where the "low oxygen" zone should likely begin and harbor non-obligate faculative anaerobes.
***
Ok, another blind assumption that the low oxygen layer will begin where you want it to. Are you going to insist it happen right there?
The interface area between aerobic and anaerobic areas is going to depend on the flow of oxygen by whatever means into the substrate.
Factors that will affect the oxygen content in the water?
inflow of oxygen from water column (how much water is being pulled into the substrate, and what oxygen concentration does it have to begin with, frequency of )
oxygen consumption by aerobic bacteria in the substrate (determined by food sources for aerobic bacteria, temperature, surface area for bacterial colonization)

What test are you going to perform to determine if this is the correct area for where the FAB are living? How are you going to determine if you need to
increase or decrease the wasting to move this layer up or down to fit it into this zone in the layered substrate?

Are you going to force the FAB into this area by tuning your wasting to make sure this is where the low oxygen layer stays?

On to the next assumption:
***
If the distance from the oxygen saturated surface to the beginning of anoxic sediment is made farther ( stretched by high frequency wasting ), which it will be, then the low oxygen zone of pore water will become thicker.
***
Just because drawing water down into the sediment will increase how deep oxygen permeates into the substrate, this does not guarantee that the interface layer will somehow grow.
Oxygen in the substrate is consumed by the bacteria present as they process organic wastes, so you may just end up creating more surface area for aerobic bacteria, decreasing space for the obligate anaerobes, and ending up with the same amount of FAB.

Again, how are you going to test this or confirm this is occurring?

On to the next assumption:
***
Since gobies "bite into the sand as much as 1.2" deep, that is going to keep them 1.8" away from the oolitic sand where the "low oxygen" zone should likely begin and harbor non-obligate faculative anaerobes.
***
This assumption is just blatantly wrong. The gobies may only bite down and sift a inch or so in depth, but these fish are notorious for rearranging substrate, and burrying things. Your substrate above this
oolitic layer may be 3 inches one day, and 1 inch the next due to the gobies shifting and moving substrate around as they see fit.
You are also forgetting the gobies tendency to create burrows.

In the proposed substrate model, these guys will be burrowing down to your critter barrier.

1-2 mm - 3 inches
.7 - 1.7 mm - 1.5 inches
screen with 6 mm openings
.7 - 1.7 mm - 1.5 inches
gravel membrane consisting of increasing sized particles to filter things
plenum or pvc wasting mechanism

Ok, problems with the above substrate model:

1) The critter screen is going to be a source of clogging and result in problems with your sandbed.
If you make a 6 mm mesh opening, the above substrate is going to plug your mesh, especially with force being applied to suck sediments down in the form of wasting from below.

2) The critter screen is intended to keep larger critters (the gobies) from disturbing lower levels.
This will also prevent stirring of the sand lower in the substrate by the larger sandbed critters necessary to keep the sandbed from turning into a dead zone.

Size ranges of sandbed detrivores:
http://www.reefkeeping.com/issues/2002-03/rs/index.php

A lot of the detrivores may be larger than your mesh allows, preventing them from going into the lower substrate to cleanup any detritus etc

3) You state that you want the low oxgen layer to be in the oolitic fine layer.
You expect to have a diverse sandbed fauna living in the low oxygen layer? I see this as becoming a dead zone quickly devoid of sandbed critters since there
will be little to no oxygen below the critter barrier.

4) with the critter barrier in place, and the predators to sand bed critters keeping the upper layer clean of sandbed critters, how are you going to reintroduce your sandbed critters to the lower level even assuming it can provide adequate environment for them?

5) the diameter of holes in the pvc and spacing really don't matter if you have void space around the pipes in a plenum
ldrhawkes original post about wasting from the bottom went into great detail that doing so will result in channeling through the substrate above. It was why he recommended making the pipe to draw from in the first place, and burrying the pipe in the substrate. Now if this is all true, who knows, but if you have a gravel filter above the PVC tubes, and void space around the PVC, the holes in the PVC are not going to create localized suction through the sandbed through distinct points, you are going to create a generic lower pressure under the entire sand bed which will be released through the path of least resistance. This is channelling.

Anyone trying something like this setup good luck.
I hope it does work.
Hopefully you will keep good notes and test appropriately to document the benefits of setting up a system like this, or if it doesn't work, maybe your measurements can point to the reason it failed.

Cheers,
Doug

[barryhc]

If you would like to discuss this Doug, I would be happy to do so. You have not discussed anything yet. You have only debated, and I don't put up with that.

Every question that you asked in your last post has already been explained by me in previous posts in this thread, which you claim to have read. I will certianly point you to at least 20 of them, if I feel that you are becoming sincere in your quest for knowledge.

If you would like to pick a SINGLE point of contention to discuss, I will happily respond to it, IF you will in like kind, respond to the answer that has been given to you. I have requested this of you already, and you have not responded.

Have you reviewed any of the "SRB" or "BPR" threads yet, that I offered you? They really cover a lot of territory, and I look to them and everywhere else I can to gain enough knowledge to further my efforts in reef keeping, including this EXPERIMENT.

I am quite sure that we will succeed here in improving the long term reliability of a sand bed. I do not know yet if we can improve any of the nutrient or compound processing capabilities, but I am working on being able to do so.

Relax a little bit Doug, it is good for you. > barryhc

[salty joe]

Posted by Doug.

At one point in the thread, it was stuff accumulating in the bed like P, at one point it is possibly heavy metals, and most recently your accepted cause of DSB tanks crashing is H2S gas nuking the tank.


It is generally assumed, at least by me, that all sorts of nasties accumulate in a sand bed. I think the idea is to drain them out from the bottom, and if there is some channeling, as surely there will be, rely on diffusion.

Also by Doug.

5) the diameter of holes in the pvc and spacing really don't matter if you have void space around the pipes in a plenum

I am by no means an expert in fluid dynamics, but I think this observation might be right on the money. It seems that the entire plenum area would be under negative pressure and the pull would be fairly even across the bottom of the sand bed. If you keep burrowing creatures like jawfish, as I plan to, there will be channeling. At least that's how I see it.

Posted by Barry.

If you would like to pick a SINGLE point of contention to discuss, I will happily respond to it

I agree, a lot of these issues are complicated. I know that I would get more from the thread if we kicked around fewer things at a time, but in much greater detail.

It is my understanding that the majority of phosphate in the sand bed is from luxury uptake by bacteria. It is also my understanding that once the bacteria run out of real estate, phosphate leeches back into the water. Assuming this is true, I would expect phosphate to concentrate in the plenum area because there are no corals or algae to mop it up, only bacteria. So it makes sense to me to make periodic draws from the plenum area. If channeling occurs, the plenum will be partially filled with clean water. Then diffusion will pull the nasties from the sand bed until equilibrium.

Assuming that this is correct, I would expect to be removing a lot of bacteria every time a draw is taken from the plenum. It would be interesting to test for phosphate, then microwave the plenum water to kill and burst the bacteria. Then shake it up real well and retest for phosphate to see if there is an increase.

Joe

["Umm, fish?"]

Joe--

Do you know what my wife would do to me if I got near our microwave with that nasty plenum water? I'd be looking for a new place to set up my tank!

You sound dead on to me. I don't think there needs to be any one reason we draw this water out. I think we can certainly do it for several reasons.

Thanks!

Andy

[salty joe]

[QUOTE]Originally posted by "Umm, fish?"
[B]Joe--

Do you know what my wife would do to me if I got near our microwave with that nasty plenum water?


I know what you're saying. My lovely wife was ready to murder me when she caught me with some really stanky stuff in the blender.

[barryhc]

Originally posted by salty joe

It is generally assumed, at least by me, that all sorts of nasties accumulate in a sand bed. I think the idea is to drain them out from the bottom, and if there is some channeling, as surely there will be, rely on diffusion.

The diameter of holes in the pvc and spacing really don't matter if you have void space around the pipes in a plenum.

I am by no means an expert in fluid dynamics, but I think this observation might be right on the money. It seems that the entire plenum area would be under negative pressure and the pull would be fairly even across the bottom of the sand bed. If you keep burrowing creatures like jawfish, as I plan to, there will be channeling. At least that's how I see it.

A lot of these issues are complicated. I know that I would get more from the thread if we kicked around fewer things at a time, but in much greater detail.

Thanks Joe, let's give it a try.

I expect there may be some channeling in the substrate, whether the draw is frequent, or occasional. I think it might be more noticable for occasional draws, because more time has been allowed for the activities that cause clumping to occur.

I have put a good deal of effort into the layering model that I have offered, to address various potential problems that might occur in the substrate, and channeling is one of them.

The layering model I have offered, is, as I have stated, an educated estimate, or GUESS, as to what might be found as beneficial to the wasting concept, and for my case of course, I'm still concentrating on the "Frequent" version, so something different might be better for Occasional Wasting.

In fact, something different might be better for Frequent Wasting as well, but nothing else has been offered. I have been searching all over the place for any inormation that would help to develop a better model, but this kind if information is very difficult to come by.

In any case, back to channeling. It will be more prevalent for sure if critters that clear large areas of substrate for their dwelling, are allowed to dig in the substrate, and it will be even worse if they are allowed to get near or close to the plenum. This is of course the function of the critter screen.

I have proposed 6mm oprnings in this screen, at midway in a 3" depth of "oolitic", or maybe slightly coarser sand. That is a .240" opening, which will certianly stop fish and large substrate disturbing animals from going further, but which will allow nearly all other types of "fauna" to pass through, and do whatever "work" they are good at deeper into the bed.

This size will also certainly not contribute to any clogging of the substrate by way of particle migration and so, is an aid to avoid "clogging" and subsequent "clumping" of the substrate. Other mechanisms can contribute to clumping, but this screen won't be one of them.

Now Jaw fish are probably the worst in this respect, and they are one of my favorites as well. I have previously posted many times, that I believe a seperate area, designed to accomodate the needs of this animal, might be set-up during initial aquascaping, to help with the cave building of this animal, and Tom at Inland Aquatics has some good information on how to go about this.

The reason for the top two layers being so deep in combination, is to promote more solids processing in the somewhat larger substrate, before it gets to the finer sand, which finer sand is much easier to "clog and clump". This would mean more dissolved nutrient processing VS solids in the finer substrate, to some degree, and should be a net benefit.

I ran the layering scheme for the first three layers, past one of the gurus in the expert forum recently, and his response was that it should not cause any trouble at all. "Fauna" and bacteria will "work just fine in this".

I still believe that as much solids as possible should be kept from ever getting to the substrate, by high flow, and removed by mechanical means, or skimming.

Filter floss, that is replaced a couple hours after feeding, and this being done everyday, is an excellent method for this if you are at the aquarium for a while, a couple of times a day, and put in a filter that is convenient for replacing floss. This will vary for some people depending on the species that they keep. Dendros, for example, like things very dirty, for the most part, and are probably not as conducive to this type of set-up. Gorgonians as well.

Gobies do not cause nearly as much trouble here, and are not likely to make it down past the bottom of the first two layers, and then into the much finer third layer, and this is one of the primary functions of the top two layers. IF, the finer third layer remains relatively undisturbed by the larger "burrowers", then the effect on channeling will be minimal.

Now about the void space. I started with the void space, as described for standard plenums, when I set-up my hex tank, about 10 mos. ago. It has pros and cons just like everything else.

On the pro side of course, it provides a good deal of balancing the flow, and can reduce the complexity of the plumbing, which I notice is bothering some people a little bit.

On the con side, it might contribute to some different chemical or bacterial processes that we find that "we", or the tank don't "care for".
"Goemans" thinks it is helpful, but not with finer substrates, and I was never convinced of the "standard plenum" concept anyway.

The latest layering model that I offered, includes a final optional layer, of 8-12mm stuff for those who may want to eliminate the void space for whatever reason, and it would be highly conducive to eliminating the channeling that is promoted by the eggcrate and void space. I am beginning to like this idea better myself, but I only started considering it a couple of days ago.

I think this is how LdrHawke saw it as far as the void space and channeling, and he may very well have been right on this one. It may not need to be any larger particle than the 5mm that is already there either. This might further reduce channeling, but the elimination of the void space and 5mm also starts to require many more holes, closer together, as I already reccomend, and that bothers some people as well.

Diffusion will be going on all over the place, and will be a great benefit of course in all respects, but I can't really describe it in detail for this scenario yet. ( maybe never )

Lot's of testing is highly beneficial for any new endeavor, and we will keep discussing this aspect for a long time, I am sure.

This is how I understand channeling at the present time, and I remain open as ever to new and better ideas.

Thanks again, > barryhc

oopS: I missed the last couple of replies from "fish" and "Joe" while typing this, so I hope it doesn't sound contrdictory to these last posts.

[barryhc]

My wife hasn't gotten to smell much of the "stanky stuff" yet, I'm sure I'll be restricted from the kitchen once she does.

My biggest problem with "Honey-wonder" though, is how paranoid she get's when she can't find one of the animals.

She has gotten to be a pain for the last couple of weeks trying to find our new little Snowflake eel everyday. I only feed him every other day, and he doesn't come out that often until he smells "Krill".

It's like one of the kids is lost or something, until I can show his little head sticking out somewhere.

You guys ARE letting the wives pick out the animals, now aren't you?

> barryhc

["Umm, fish?"]

I think that part of the problem we are running into in this discussion is that everyone is picturing these bacterial layers in terms of Euclidean flat planes. You have _this_ plane on top of _this_ plane and god forbid if the two ever mix. Don't disturb the planes!!!

I don't believe channeling matters, to a certain extent. Picture a cross-section of the sand bed. Suppose we have a roughly cone-shaped channel cutting through the sandbed top to bottom. Inside this channel will be an aerobic zone. This will also be a good place to find food. Aerobic bacteria will migrate to this zone because it has what they need no matter what the depth. Outside of this zone will be aerobic (near the surface of the sand bed, as normal), anaerobic, or anoxic as normal (if we are not managing to pull water through that section).

Oh, no. We aren't draining the sandbed evenly. Who cares? All evidence so far points to the fact that sandbed nasties make their way to the bottom. As long as we're draining the bottom, what difference does it make how the water that replaces it gets there?

Personally I hope that I disturb the sandbed somewhat when I make my infrequent draw. My intention is to clear real estate for bacterial population expansion. Since I am couting on channeling, I'm also counting on my draws eliminating some of the low- or no-O2 bacteria but leaving enough undisturbed to allow for quick population recovery as the O2 levels re-stabilize.

A whole lot like harvesting macroalgae....

[barryhc]

Originally posted by "Umm, fish?"
I think that part of the problem we are running into in this discussion is that everyone is picturing these bacterial layers in terms of Euclidean flat planes. You have _this_ plane on top of _this_ plane and god forbid if the two ever mix. Don't disturb the planes!!!

Well, I both agree, and disagree. Let me explain. You are quite right in my opinion, about the planar concept. It is there in some places, and not in others. Where it is planar, that just means fairly even, in terms of depth, but much of this is a "contiuous gradient" and "in flux", especially during the "wasting" which I am counting on. And it isn't necessarily even everywhere, but I don't think it has to be. The bacteria are very adaptive.

The "balancing" that I have ranted on about is intended to keep these variations fairly small, not nonexistant, and primarily, not "very large", as in several inches or more. Even then you may be right that there is a different shape to these zones, but diffusion certianly does not need to be "vertical", and I think this is what you're getting at, horizontal or angular diffusion around one of these vortex areas should work rather well also.

Personally I hope that I disturb the sandbed somewhat when I make my infrequent draw. My intention is to clear real estate for bacterial population expansion. Since I am couting on channeling, I'm also counting on my draws eliminating some of the low- or no-O2 bacteria but leaving enough undisturbed to allow for quick population recovery as the O2 levels re-stabilize.

I agree again, I am expecting this same thing to occur as well, whether I am drawing 6 times a day, or once a week. I am going to have to learn about this through testing and experimantation.

So, the "excessive" efforts I am putting into avoiding channeling, to some degree, may not end up being critical to the success of the system, but I don't see them as being particularly detrimental, do you?

Thanks for the post, and I haven't gotten to see your new pictures yet, I' m going to go look right now.

Happy Reef Keeping! > barryhc

[barryhc]

I guess another way to look at this, is like "Umm-fish"? stated before, if it doesn't do any good we're out some time and some cost for PVC etc., but we still have a sandbed, and they are pretty good to begin with.

I cannot imagine that we have somehow created a monster that causes our sandbeds to become "animal assasins", or whatever. Some "yuck" is going to come out with the "waste water", and that will be a net plus. Even if improved Nitrate and P processing were found to be minimal or nonexistant, I still believe that some of the nasties that are removed, would help to avoid the "crash" that is OCCASIONALLY reported, even if only to a minor degree.

I still have much higher hopes for this system than that, and I wiil state so here again. It won't happen in a few months . . .golly gee!!!

This is going to work!

None of us are touting this as a "magic bullet", or proposing to eliminate other systems in preference to this concept. It's just another of many tools available to keep things stable, at least as I see it.

Happy reef-keeping! > barryhc

["Umm, fish?"]

Right, barryhc, but I'm refering to a planar mental block. I don't think our sandbeds have these perfect little layers, but that's the way people think about them. And I think that the mental block and people's reluctance to let go of it is harming a lot of the recent discussion.

Well, I both agree, and disagree. Let me explain. You are quite right in my opinion, about the planar concept. It is there in some places, and not in others. Where it is planar, that just means fairly even, in terms of depth, but much of this is a "contiuous gradient" and "in flux", especially during the "wasting" which I am counting on. And it isn't necessarily even everywhere, but I don't think it has to be. The bacteria are very adaptive.

No, I don't think your efforts to avoid channeling will be detrimental.

The only real problem I can think of with this is only really a problem for frequent wasting ( ). Thought problem: We are relying on diffusion to send all the nasties down to our manifolds. But what are these nasties displacing? By constantly sucking a bunch of O2 rich water down channels to the tank bottom, will we see a diffusion of O2 rich water back up through the sandbed? I think this is kind of Doug's point (or at least one of them ): will this process lead to a completely aerobic bed?

But, I know that you are planning to remove minute quantities of water with each draw and I assume the O2 will be used up relatively rapidly from bacteria around the channels in the sandbed and along the plenum, so I don't think it's a horrible problem as long as you don't over-waste.

I wish we could see what's going on down there. What if you wound up with a top and bottom aerobic layer (here's me coming in with a planar concept, per above discussion ) sandwiching an anaerobic and anoxic zone? What the heck would that do?

[barryhc]

Originally posted by "Umm, fish?"
I think that's the mental block and people's reluctance to let go of it that is harming a lot of the recent discussion.

No, I don't think your efforts to avoid channeling will be detrimental.

Thanks, I needed that, I was about to have a crying spell!!

The only real problem I can think of with this is only really a problem for frequent wasting ( ). Thought problem: We are relying on diffusion to send all the nasties down to our manifolds. But what are these nasties displacing? By constantly sucking a bunch of O2 rich water down channels to the tank bottom, will we see a diffusion of O2 rich water back up through the sandbed? I think this is kind of Doug's point (or at least one of them ): will this process lead to a completely aerobic bed?

Absolutely not, I will test for it ( oxygen ) with some type of probe or "water collector" as I have described previously, to determine, and modify oxygen levels so that this condition that you are concerned with does not occur. I am concerned with this as well, and I WILL NOT LET IT OCCUR!!!!!!!!!!!!!!!!!!

But, I know that you are planning to remove minute quantities of water with each draw and I assume the O2 will be used up relatively rapidly from bacteria around the channels in the sandbed and along the plenum, so I don't think it's a horrible problem as long as you don't over-waste.

I at least, certianly will not "over-waste". Only that amount that is conducive to controlling the oxygen gradient to a depth that is considered to be beneficial to "stretching" the "non-anaerobic" populations will be utilized, and the Anaerobic population will become "somewhat thinner", not non-existant.

I still plan to target the beginning of the anaerobic zone at somewhere near the beginning of the oolitic layer of sand, and could most certianly turn out that is not the best place for it, or the best depth of oolitic sand, but is still my best guess, and until some better method is identified, I still currently plan on using this model.

If this model has a flaw, or more importantly, a betterment, that I or anyone else can identify, I will adjust my thinking to be sure.

Remember, that at the 7/64" depth of "column water" for each draw, that I am still currently proposing, the draw depth within the substrate will be about 7/8", and it is the recovery rate of the bacteria, or the time it takes them to consume the oxygen in this 7/8" deep layer that has recieved oxygen, at whatever depth that this happens to be, that wiil cause a necessary modification to the wasting "schedule".

The bottom layers of coarser gravel, along with the tight packing of the feeder tubes, as I have shown in the 55 gal. graphics in my gallery, will cause these vortex shapes to overlap, long before they get to the bottom of the oolitic layer of sand, and most of the oolitic layer should also remain relatively undisturbed, so most of any channeling is going to occur above the oolitic layer, and the oolitic layer itself helps to even this out before any flow gets to the bottom of it.

Please note that I have the feeder holes, only in the bottom of the feeder tubes, and pointing therefore at the glass, which is going to eliminate nearly all funnel shaped activity of the water flow in the plenum area.

Now, if you actually prefer these funnel shaped oxygen gradations in your substrate, they are easy to promote, as you have pointed out, you just have to decide how you will control them if at all, and that MIGHT BE a little more complex. ( If I meant "would be", I would have said WOULD BE, but I don't usually play those kind of games )

I have actually done some thinking along these lines, and I think the concept could have some merit, but it would certianly be a lot more difficult to test for, and so I have avoided even discussing it thus far.

Above the oolitic layer is the somewhat coarser layers 1 and 2, which should remain primarily aerobic anyway, which is one of the things that I have to test for to modify the wasting volume and frequency schedule. Without this testing and schedule modification all kinds of "who knows what" might occur.

I wish we could see what's going on down there. What if you wound up with a top and bottom aerobic layer (here's me coming in with a planar concept, per above discussion ) sandwiching an anaerobic and anoxic zone? What the heck would that do?

I will check to see what is going on down there, by way of water testing at many depths in the substrate, at least one per inch of depth.

Check the Biological Phosphate Removal thread that I have referred to, there is some terribly interesting concepts going on in waste management, that have to do with modifying the oxygen level back and forth in a substrate, in order to force both denitrification and puosphorous removal to occur biologicaly, and at a much higher rate, for both the phosphorous and the nitrate.

Many of these systems have been up and running for many years, and are accepted methodology. Fresh water is not the same as saltwater, but it isn't that far off either.

There is a new version, just out, that uses a single stage, and only changes back and forth between Aerobic and Anaerobic conditions, over periods of less than several hours, which is exactly what will happen with frequent wasting.

Thanks again Andy, > barryhc

[salty joe]

Posted by Barry

I have proposed 6mm oprnings in this screen, at midway in a 3" depth of "oolitic", or maybe slightly coarser sand. That is a .240" opening, which will certianly stop fish and large substrate disturbing animals from going further, but which will allow nearly all other types of "fauna" to pass through, and do whatever "work" they are good at deeper into the bed.

I think that this is an outstanding foundation for a sand bed of this type. Also, the idea of using progressively larger gravel and sand to block fine sand from the plenum is very ingenious. Before I started reading this thread, I was beating myself up trying to find some kind of membrane to do just that.

When I set up a plenum, and I can always change my mind, but at this point I am leaning toward a void space with a sand bed suspended above, without PVC. With this type of set up, I think perhaps a slow draw would be beneficial in that it would minimize channeling.

This is exciting because it's new and I honestly believe that we are onto something. This is a great thread and I thoroughly enjoy it.

A snowflake eel, huh? Very cool fish. I had one for 11 years and I might still have it today excepted it jumped out. And I thought I had my tank very well covered. He slipped out of a hole I had made for the heater wire. I noticed as he grew larger he became a lot less shy. And when he was hungry he got real rowdy. He was hungry when he jumped.

Joe

[barryhc]

Originally posted by salty joe
A snowflake eel, huh? Very cool fish. I had one for 11 years and I might still have it today excepted it jumped out. And I thought I had my tank very well covered. He slipped out of a hole I had made for the heater wire. I noticed as he grew larger he became a lot less shy. And when he was hungry he got real rowdy. He was hungry when he jumped.

Yeah, he's a bit bigger around than a pencil and about 8" long. When he finds a chunk of frozen Krill ( about 1" length of pencil dia. ), he has to "KILL IT", and I mean REALLY KILL IT TO DEATH!!!!!

The thing is, I have no cover at all on the tank, on top of which, he is always finding his food right at the surface. I might have to go back to feeding the open brain coral, and let him steal it from him, until I get the "lid" built.

Geeze, the complexity will never cease!

I'd better get on to a temporary lid, see ya. > barryhc

["Umm, fish?"]

Please note that I have the feeder holes, only in the bottom of the feeder tubes, and pointing therefore at the glass, which is going to eliminate nearly all funnel shaped activity of the water flow in the plenum area.

But, if detrius or mulm or whatever does build up down there, having the holes on the bottom makes it much more likely they will clog. I'm currently searching for a magnet with a very low profile that'll slip under the pvc pipes (the fittings keep them just off the glass) so I can stir things up.