Plenums and the wasting "option"

[wave98]

Sorry, I didn't get any pictures while the plenum was being built. I am working on getting some graphics that I have, converted into a format that I could post here. The plenum construction isn't really fancy at all though. It is built exactly as prescribed by "Goemans" for standard plenums with the following exceptions.

The plenum has an output from a central manifold that has as many feeder tubes in it as I could fit into the avail. space. It is constructed from 1/2" PVC pipe, tees, crosses, and one elbow. It just can't get any simpler than that.

The feeder tubes have a total of 72 holes at .042" dia. This totals up to .1 sq. in. of flow area. A pump outlet with 1/2" dia.( which is what I expect to use ) has an area of .2 sq. in. which gives us a .5 to 1 flow area restriction.
This causes flow into the feeder tube holes to be very evenly balanced, and is particularly conducive to maintaining a fairly even oxygen gradient in the substrate.

How deep this oxygen gradient extends into the substrate is where this thread is currently at, and we don't really have an answer right now, but "plenum wasting" allows us to modify this gradient to quite a degree while static systems like DSB and standard plenums do not.

I don't use any "formulas" per se, but I have the math available and it is very straight forward.

DonW: What measurements, and why what? Could you be a little ( or a lot ) more specific?

Mojo, "old buddy", diffusion models?

Thanks all, and happy reef keeping!

 

[wave98]

So things I learned when playing was getting the water to diffuse through the bed evenly, was a bear and I had no luck with the finer sand. the other was to find a viable system to remove the end product detritus which will eventually clog the system. I notied you mentioning frequency alot, can you tell me a little more about this?? and then if you have any thoughts on the problems I encountered.
MIke

Hey Mojo: My last post above, should represent a more comprehensive response to your first post in this thread. Let me know of course, how it does or does not help.

Happy reef keeping! Wave98

 

[wave98]

Hey MikeS, where have you been? Out of town again?

Well, when you get back( or whatever ) "poke some holes", or fire up some "diffusion goodies", enjoy!

Thanks for your input! . . . Wave98

 

[MikeS]

Sorry, been a bit distracted and busy as of late :doubt:

I'll try to get a decent reply perhaps later this evening...

MikeS

 

[wave98]

I'm looking forward to it MikeS, I think we are probably a lot closer than it might appear to some people. In any case, we're both looking at running a substrate for one reason or another, and both looking into new or modified versions of substrate systems.

I am looking at this, having noticed all the controversy through a lot ( a very lot ) of investigation, and looking for something to address some of the pitfalls that are commonly reported in the available information, while you certainly have more direct experience than I, and I am sure that that your investigations are extensive as well.

Maybe we could repost a short summary of our system objectives, with a bit of the proposed methodology, and see what comes from there. :idea:

All members running substrate systems of any kind are certianly welcome to jump in here with their system types, and experiences, good or bad. and let's see what we can learn.

Thanks all! > Wave98

 

[MikeS]

What I am looking for from this system, and this thread, is to improve NNR, reduce "deep bed nasties", and improve "substrate system" longevity

Got it, that seems the be the general hopes of maintaining any substrate system. Wave, in a nutshell, can you please explain to me why you want to do frequent drawoffs on the plenum instead of less frequent ones? I think that overy-frequent drawoffs may have some negative effects....

Anyone who believes that "substrate systems" are nothing but trouble, need to run bare bottom systems, and many do so with very good results.

It's not so much that they are trouble, it's just that so many people expect magic from them and fail to recognize that they are what they are, and they have a lifespan...many also "abuse" them by overloading the tank, not providing adequate maintenance, not complimenting the system with good flow and mechanical filtration/skimming, ect....

Finer grains at or near the surface keep detritus that is generated in the water column at a minimum. Anyone who is unhappy with "sand storms", needs to diversify their flow, and can further eliminate such "storm" problems with some "rubble", or 1-4mm "stuff" at the surface. Those who want to further cry "bloody murder" about detritus accumulation at the surface, can add a bunch of snails and crabs to keep the substrate surface, and also that of their live rock nice and clean. I would reccomend them anyway.

If the fine grains are at the surface, particularly in a system with good flow, over time you are going to experience "migration", where the fines sink to to the bottom of the substrate and the more coarse particles end up on top. Any disruption of the substrate will increase this rate of migration, such as burrowing critters, manual cleaning of the upper levels of the substrate, and also likely drawoffs from a plenum. Here's a practical example,... put some sand that has a large variation of particle sizes in a clear bucket, add some water, swirl it around for awhile, and let it settle, you'll see what I'm talking about...

Also, any fine sand barrier on the top layer that inhibits introduction of detritus, is also going to inhibit diffusion into the substrate....

I am still in the "layering camp", as far as substrates go, and that does not mean that I consider "layering" to be the easier way to go in general. It just seems to me that if we are going to be utilizing the "wasting option"( and that is what I am promoting ), with high gph rates and "high frequency" wasting schedules, that we can do some things that were not available in a "static pore water flow" system. I am insisting on a substrate selection that is conducive to sand stirring creatures( gobies and jawfish etc. ), so i just don't have the BB option.

I think that layering, particularly in an active system like a plenum wasting one, will ultimately be counter-productive and reduce the substrate lifespan. Eventually, these fine sand particles will find their way into the plenum, clogging it up. They will also hinder natural diffusion rates. Also, these fine particles will increase the likelyhood of "channeling" to occur in the substrate, creating dead spots, and this channeling will worsen over time IMO. I still say the best bet is a uniform coarse substrate, as it avoids many of these pitfalls.

In other words, dynamic and controlled flow, downward in a substrate, offers options that are simply not available in a "throw it in" and hope for the best system, which is what we are left with in a static ( no ) flow system, which is the only other option, if you intend to run a substrate, which I do.

Agreed....but the real question becomes how often and under what circumstances do we draw off the system? I'm looking at a more passive approach, deal with the nasties on infrequent basis....your approach wants to prevent the buildup of them altogether. While this has benefits, it has pitfalls as well. Look at it this way, you need the anerobic zone. And things happen more slowly down there, and require larger bacteria populations. If you are constantly adding O2 rich water to that environment, you are slowing it down even further. And by slowing it down, you are still going to have nitrate issues in the long run IMO. I really think this needs to be a passive system, not an agressive one.

MikeS

 

[wave98]

Wave, in a nutshell, can you please explain to me why you want to do frequent drawoffs on the plenum instead of less frequent ones? I think that overy-frequent drawoffs may have some negative effects....

Please read posts #4 and #14. Yeah, I know I was the one who said "repost", so here goes:

"High Frequency Wasting" is intended to simulate continuous wasting. True continuous wasting would be at very low flow, and would cause flow imbalance problems that are mechanicly insurmountable. What I hope to achieve from HFPW is extended anoxic zone with the associated faculative bacteria and denitrification, same as you Mike.

I insist on having a substrate conducive to Gobies and Jawfish as well as "whatever substrate fauna", as previously stated, and the upper substrate becomes such as is necessary.

It's not so much that they are trouble, it's just that so many people expect magic from them and fail to recognize that they are what they are, and they have a lifespan...many also "abuse" them by overloading the tank, not providing adequate maintenance, not complimenting the system with good flow and mechanical filtration/skimming, ect....

EXACTLY!

If the fine grains are at the surface, particularly in a system with good flow, over time you are going to experience "migration", where the fines sink to to the bottom of the substrate and the more coarse particles end up on top. Any disruption of the substrate will increase this rate of migration, such as burrowing critters, manual cleaning of the upper levels of the substrate, and also likely drawoffs from a plenum.

Firstly, I expect the smallest grains to be about 1mm, and that is 20 times larger than the smallest grains prescribed by DSB proponents. Let's just keep that size and relationship in mind here.

Also, any fine sand barrier on the top layer that inhibits introduction of detritus, is also going to inhibit diffusion into the substrate....

2-4mm substrate will effectively block migration of 1mm particles, in my ever so humble estimation, and that is the grain size that I am currently looking at for the area under the "sifter blocking" screen. This screen is, again, at 3" or even 4", above the "plenum".

I am, by the way, preparing, from all of this to install a 240 gal. reef tank, which will likely be in the 72" x 24" x 30" deep version, which is often times considered "too deep" in terms of volume to area ratio and lighting effeciency. So 8" of substrate depth does not bother me relative to the above concerns.

The "finer" substrate ( 1 to 4 mm ) will not inhibit diffusion into the substrate, if HFPW is utilized using high flow and a properly designed "plenum".

This is, again, the point I'm trying to get to with all of this, and we may need to carefully define "diffusion", as to that which occurs in a "static" condition, which is primarily chemical and biological, VS "advection" ( which you are counting on ), and then "forced downflow", which I am promoting.

I think that layering, particularly in an active system like a plenum wasting one, will ultimately be counter-productive and reduce the substrate lifespan. Eventually, these fine sand particles will find their way into the plenum, clogging it up. They will also hinder natural diffusion rates. Also, these fine particles will increase the likelyhood of "channeling" to occur in the substrate, creating dead spots, and this channeling will worsen over time IMO. I still say the best bet is a uniform coarse substrate, as it avoids many of these pitfalls.

Well now, I don't see it that way as per above, although I acknowledge that the layering doesn't particularly make it "easier", but again, there are specific flow restriction requirements that must be included in the "plenum" design in order for "balanced flow" to occur in the plenum area and then in the substrate above it.

Originally Posted by wave98
In other words, dynamic and controlled flow, downward in a substrate, offers options that are simply not available in a "throw it in" and hope for the best system, which is what we are left with in a static ( no ) flow system, which is the only other option, if you intend to run a substrate, which I do.

I just had to throw that in again, and as I continue to remind everyone here, I insist on supplying a substrate to the substrate dwellers that I love, and I have no choice here ( at the surface ).

Still, I, we, whatever, can have a "system" that operates under the "mess at the top", if we utilize a forced downflow system that causes good anoxic conditions to prevail in the lower levels of the substrate.

Agreed....but the real question becomes how often and under what circumstances do we draw off the system?

EXACTLY! That is the question that I am most looking into here.

I'm looking at a more passive approach, deal with the nasties on infrequent basis....your approach wants to prevent the buildup of them altogether.

I do hope to reduce the nasties on a continual basis, and to prevent some portion of their build-up. The emphasis is, however, more on the extension of the anoxic or low oxygen zone, the same as you.

While this has benefits, it has pitfalls as well. Look at it this way, you need the anerobic zone. And things happen more slowly down there, and require larger bacteria populations. If you are constantly adding O2 rich water to that environment, you are slowing it down even further.

I certianly do not intend to introduce O2 rich water into the anaerobic zone, but there is no known value for how deep the aerobic and anoxic zones extend into the substrate. That value would be variable to say the least, and quite dependent on such factors as grain size, water column flow ( supporting "advection" at larger grain sizes ), "critter populations" both bethnic and stirring types, etc.

Goemans thinks he has it "nailed" at 2-4mm and 4" depth with plenum and no sand stirring creatures. You are liking 3-5mm with a depth of 6". I have no complaints with either of these.

The frequency and volume that is required of a wasting plenum, that will promote anoxic conditions to a proper depth, is not known, and I am looking into what those parameters might be.

There is no black or white here, only "shades of gray". I don't have the answers to all of these questions, but I am looking for them. It will take some experimentation and a goodly amount of time, to reach some conclusions as to how we can help our wide variety of reef keeping requirements.

I still believe that "wasting plenums" offer some possibilities and adjustability to us that static systems do not. The substrate size and depth considerations will inspire controversy forever, and more power to us all because of it!

Thanks MikeS, and all . . . Happy reef keeping > Wave98

 

[MikeS]

What I hope to achieve from HFPW is extended anoxic zone with the associated faculative bacteria and denitrification, same as you Mike.

Well...to be honest, I'm not really concerned with the transitional anoxic zone. My main goals are to have a nitrate reducing substrate that is not greatly reliant on critters like a DSB, the coarse substrate and high flow will facilitate diffusion in my setup instead. As for wasting, I'm looking at a setup that will allow me to help rid the system of accumulated byproducts from time to time, not one that prevents them altogher (mainly because I'm not entirely sold on the compromise yet...)

Firstly, I expect the smallest grains to be about 1mm, and that is 20 times larger than the smallest grains prescribed by DSB proponents. Let's just keep that size and relationship in mind here.

Got it...you are still going to experince a degree of migration, reguardless of particle size, as a function of your flow and disruption of your substrate...the finer the particles versus your flow and disrtuption, the more pronounced the migration, and hinderence of diffusion in the long run...

2-4mm substrate will effectively block migration of 1mm particles, in my ever so humble estimation, and that is the grain size that I am currently looking at for the area under the "sifter blocking" screen. This screen is, again, at 3" or even 4", above the "plenum".

Hmmm...it's not going to totally block it...it may slow it down, but it won't block it. The screen will help, but that has it's own set of issues as well, ie clogging, channeling, ect IMO....

The "finer" substrate ( 1 to 4 mm ) will not inhibit diffusion into the substrate, if HFPW is utilized using high flow and a properly designed "plenum".

In a perfectly designed system, maybe not, but I still think realistically the finer particles will inhibit mechanical diffusion, and this inhibition will increase over time. This is where I think the coarse substrate has some marked advantages...less pronounced effects on diffusion due to migration, less chances of channeling, ect...

MikeS

 

[wave98]

"Alrighty then".

I'm doing it so I can "refresh" the system from time to time, remove some detritus and byproducts, ect. in an attempt to lenghten the effective lifespan of the system. I still think we need to get deeper into the effects of low oxygen (not deviod mind you) on nitrate reduction.

As stated above, I think we need to clarify "anoxic" (ie low oxygen) and how this aids/hinders denitrification, and we need to talk a bit about the mechanical issues of frequently drawing off the plenum and possible detritus compounding...

Well...to be honest, I'm not really concerned with the transitional anoxic zone. My main goals are to have a nitrate reducing substrate that is not greatly reliant on critters like a DSB, the coarse substrate and high flow will facilitate diffusion in my setup instead.

H-m-m-m . . . Well, OK. I am also interested in a nitrate reducing substrate, whether or not it has critters. In my particular case, it does have critters ( micro fauna, whatever fauna ), and they are of some benefit to be sure, but "the system" does not need to be reliant on them.

Again, as I continually restate, my first interest in a substrate is to offer a habitat for the creatures that require it, again, gobies, jawfish, maybe cukes, clams and LPS etc. Some of these may not be helping very much, but for the time being, I insist on giving them an environment to live in, and I just don't have the specific choice that MikeS is pursuing, available, for that reason. :exclaim:

I am further presenting a possibility as to how that might be done, while retaining the best portions of substrate denitrification that I can, along with some "nutrient and nasties" export through "wasting". :idea:

Even Mojo seems to think that some improvements to oxygen gradients might help to avoid some of the P leaching, and I happen to agree.

As for wasting, I'm looking at a setup that will allow me to help rid the system of accumulated byproducts from time to time, not one that prevents them altogher (mainly because I'm not entirely sold on the compromise yet...)

I do hope to reduce the nasties on a continual basis, and to prevent some portion of their build-up. The emphasis is, however, more on the extension of the anoxic or low oxygen zone, the same as you.

Whoever said "eliminate altogether", I still don't get that one.

2-4mm substrate will effectively block migration of 1mm particles, in my ever so humble estimation, and that is the grain size that I am currently looking at for the area under the "sifter blocking" screen. This screen is, again, at 3" or even 4", above the "plenum".

Hmmm...it's not going to totally block it...it may slow it down, but it won't block it. The screen will help, but that has it's own set of issues as well, ie clogging, channeling, ect IMO....

It is the 2-4mm substrate that will "block" ( or inhibit ) "finer particle" migration, and upon further investigation, it turns out, that evenly graded 4mm substrate will inhibit this particle migration down to particles as small as .3mm. That "reads" three tenths of one mm.

Now if "substrate melting" is your concern, then you need to realize that the lower substrate at 2-4mm ( or whatever size you use ), is going to "melt" also, and will retain most of this "small particle migration" blocking mechanism.
This will not cause "clogging" at the "finer to larger substrate interface". I say again, this will not cause clogging! :exclaim:

As far as the "sifter blocking screen" goes; This is a screen to block "creatures" from disturbing the bottom 3 to 4 inches of substrate. It has nothing to do with "particle migration". I think 5-6mm grating holes would do fine, and will have no effect on anything ( diffusion, particle migration, denitrification or anything else! ), other than "creatures".
So you see, I am putting together a "creature playground" at the surface, and basicly a standard plenum under that, with the added benefit of being able to force "diffusion" if you like, to occur, even though there is a "playground mess" above it.

The "playground' portion will function much like an average between DSB and standard plenums ( which both work to some degree ), but now we are not left with just that, but we have "some bit of control" over "diffusion rates" and or "Oxygen gradients" if you prefer.

In a perfectly designed system, maybe not, but I still think realistically the finer particles will inhibit mechanical diffusion, and this inhibition will increase over time. This is where I think the coarse substrate has some marked advantages...less pronounced effects on diffusion due to migration, less chances of channeling, ect...

I understand the concerns that you have been having in this regard Mike, really, and that is where I started with this, some time before I came to this forum. I have been very hard at work on this for a very long time, and I am not nearly done.

I think that the system that you are considering Mike, is reasonable actually, for what you want from it IMO, and at least with a "Wasting Plenum", you have some measure of adjustability, if you so desire.

I must point out here, that whatever avoids "diffusion inhibition" will also inhibit "detritus rejection" as well, so that is a double edged sword, unless of course you force "diffusion" through a "detritus rejecting upper substrate" by using "forced downflow" etc.. :idea:

Now, about the "Anoxic Zone", "advection flow", "denitrification" and the aid or hindrance thereof, and what is occuring in the "anearobic zone", good and or bad, but based on current understandings of there being an anoxic zone to consider, and carefully, not from publications or information that do not acknowledge the "anoxic zone". Or at least "salted" with that consideration in mind.

This is just about where we thought we had started at, but I'm open to discussion on anything at all. There is no competition going on here that I am aware of, at least not on my part.

Come on people, "throw in the whole bag of worms" here, there is nothing to gain or lose here, but "knowledge" or "face". The knowledge is important and the face is not IMHO.

Wave98

 

[MikeS]

H-m-m-m . . . Well, OK. I am also interested in a nitrate reducing substrate, whether or not it has critters. In my particular case, it does have critters ( micro fauna, whatever fauna ), and they are of some benefit to be sure, but "the system" does not need to be reliant on them.

Ok, we both seem to be in agreement on that point, the less reliant the system is on bugs and worms the better.

Again, as I continually restate, my first interest in a substrate is to offer a habitat for the creatures that require it, again, gobies, jawfish, maybe cukes, clams and LPS etc. Some of these may not be helping very much, but for the time being, I insist on giving them an environment to live in, and I just don't have the specific choice that MikeS is pursuing, available, for that reason.

Hmmm...well, we may be closer than you think on that one my friend, look at my tank (in my signature)....I have an LPS tank, with a large t. derasa, and other "substrate dwellers" like conch, bubbles, ect....Of the creatures you listed, with the possible exception of the cuke, I don't think any of them particualrly require a really fine substrate, a uniform 2-4 or 3-5mm should suit their needs just fine IMO, and you avoid the pitfalls of layering of different gradations of substrates. For burrowing critters like jawfish and gobies, a simple screen or some eggcrate should do the trick.

Whoever said "eliminate altogether", I still don't get that one.

I didn't.... Perhaps "prevent" was the wrong term to use. It just seems to me that small, frequent drawoffs would be geared more towards slowing the buildup in the first place (not necessarily a bad thing mind you) rather than larger, less frequent drawoffs that would reduce them after the fact so to speak. While slowing the buildup as much as possible is a good thing, there are IMO other ways to do this, namely good mechanical removal of waste BEFORE it becomes a problem (back to my point about this system complimenting the tank as a whole). In a small, more frequent drawoff setup, you are probably going to be introducing more oxygen into the substrate top to bottom. All good in the upper levels, but what about the impact on the anerobic zone itself? Also, I still think a system with more frequent drawoffs will be more likely to accumulate detritus than one without, ultimately making the effort somewhat self defeating. Just my opinion, mind you...

It is the 2-4mm substrate that will "block" ( or inhibit ) "finer particle" migration, and upon further investigation, it turns out, that evenly graded 4mm substrate will inhibit this particle migration down to particles as small as .3mm. That "reads" three tenths of one mm.

Ok...now for that to be true, one would have to assume that the 2-4mm substrate is going to remain completely undistrubed and static as placed, which simply isn't going to happen. Lots of things are going to disturb it, like burrowing critters, maybe manual cleaning of the upper layers, strong flow, ect, ect, ect...the list goes on and on. I'm not saying this migration is going to take place overnight, it won't...it's a function of time vs. disruption. And this disruption won't occur evenly across the entire substrate either, some areas will recieve much more disruption (and therefore much more migration) than others. This is why I don't like the idea of particles finer than 2-3mm. The smaller the particle, the inhibtion, trapping, channeling, dead spots, ect will occur as I see it.

Now if "substrate melting" is your concern, then you need to realize that the lower substrate at 2-4mm ( or whatever size you use ), is going to "melt" also, and will retain most of this "small particle migration" blocking mechanism.
This will not cause "clogging" at the "finer to larger substrate interface". I say again, this will not cause clogging!

Again, you are still working under the assumption that the 2-4mm substrate will remain static and undisturbed, which it won't.

As far as the "sifter blocking screen" goes; This is a screen to block "creatures" from disturbing the bottom 3 to 4 inches of substrate. It has nothing to do with "particle migration". I think 5-6mm grating holes would do fine, and will have no effect on anything ( diffusion, particle migration, denitrification or anything else! ), other than "creatures".
So you see, I am putting together a "creature playground" at the surface, and basicly a standard plenum under that, with the added benefit of being able to force "diffusion" if you like, to occur, even though there is a "playground mess" above it.
The "playground' portion will function much like an average between DSB and standard plenums ( which both work to some degree ), but now we are not left with just that, but we have "some bit of control" over "diffusion rates" and or "Oxygen gradients" if you prefer.

I get what you are saying...sorry for asking for a re-post, exactly how deep do you plan on making your substrate here?

I must point out here, that whatever avoids "diffusion inhibition" will also inhibit "detritus rejection" as well, so that is a double edged sword, unless of course you force "diffusion" through a "detritus rejecting upper substrate" by using "forced downflow" etc.. :idea:

I agree 100%, it's a double edged sword...now the question becomes, which edge of the sword would you rather deal with? Inhibit detritus introduction and you also inhibit diffusion. Promote diffusion and you promote detritus introduction. Ok...we want good diffusion, right? So let's deal with the detritus and waste....how about dealing with as much of it as we can mechanically BEFORE it becomes a problem in the substrate? With good flow, skimming, no overstocking/overfeeding, manual cleaning of the upper layers, ect...

MikeS

 

[wave98]

OK, Mike, I think we are starting to make some progress here.

Ok, we both seem to be in agreement on that point, the less reliant the system is on bugs and worms the better.

EXACTLY!

I like the bugs and critters because they are interesting, and in many cases, they do help. I think that we should learn enough about these animals to pick the ones that help the most and try to avoid most of the ones that don't.

Relying on them ( or anything else for that matter ), to the point of excluding other valuable "system maintainence" features, good husbandry or equipment, is likely ( along with poor husbandry in some cases ) to have been the cause of many failed systems and indeed much of the controversy that still abounds regarding substrate, refugiums, filtration, UV, charcoal, skimming, lighting; GEEZE! You name it!

Hmmm...well, we may be closer than you think on that one my friend, look at my tank (in my signature)....I have an LPS tank, with a large t. derasa, and other "substrate dwellers" like conch, bubbles, ect....Of the creatures you listed, with the possible exception of the cuke, I don't think any of them particualrly require a really fine substrate,

Well, Exactly again, except that I have already been trying to explain to you just how close we are. . . . And it's not just on "that one".

Nice tank and creatures by the way! I particularly like your DIY "skimming intake" to the HOT filter. I've been threatening to make a similar modification to my "sea-clown" skimmer for the same purpose of gas exchange, as well as taking that crud directly to the skimmer. I see you've made some modifications to the skimmer and I'm particularly interested here, because the
adjustment on the "as purchased" skimmer $ucks, and I'm not happy about the micro bubbles either.

I'm curious too, about your carbon use as well. I agree with carbon use as well, although I'm a bit hesitant to run it 24/7. HEAVEN FORBID, that we should ( or not ) ever discuss Tri Based Carbon Pellets ( "TBCP" )!

Geeze, I think I saw some "razor calupera" or something similar go "sexual" over the weekend. What a chemistry set, Heh?

Well, I appear to digress here, but in fact Mike, we appear ( to me anyway ) to be very close indeed!

Well, alright, back to the "discussion".

Perhaps "prevent" was the wrong term to use. It just seems to me that small, frequent drawoffs would be geared more towards slowing the buildup in the first place (not necessarily a bad thing mind you)

Well, that is kind of how I have been looking at it.

While slowing the buildup as much as possible is a good thing,

Yeah?

there are IMO other ways to do this, namely good mechanical removal of waste BEFORE it becomes a problem (back to my point about this system complimenting the tank as a whole).

EXACTLY, AGAIN!

In a small, more frequent drawoff setup, you are probably going to be introducing more oxygen into the substrate top to bottom. All good in the upper levels, but what about the impact on the anerobic zone itself?

OOps! ! ! ! . . . . . No actually. It is the frequency and volume of "the draw", that will determine how the oxygen gradient is affected by "wasting".

Firstly, it is my main endeavor here to learn enough about "Oxygen Gradation" to take an "educated estimate" as to how deep this oxygen gradient exists in a given substrate in a "normally static" ( unforced ) condition.

THEN, a person could take an "educated estimate" as to how this oxygen gradient might be affected by "wasting the plenum". The bacteria colonization is going to be affected by this "gradient", AND, modifying it by "wasting" is going to cause better or worse modification to occur in the bacterial colonies, and there are a lot of bacterial colonies "in there"!

Secondly, No again, it is all of my effort here, to learn what I can, to specifcly not create a "new version of undergravel filter"( bio-balls will do this quite nicely for a lot less trouble )!

And so, what about the "anearobic zone"? I certianly intend to maintain however much of that as I find to be advantageous ( and waste however much I don't ), along with considering the "anoxic zone" that you, Mike, were once interested in. I am certainly interested in it!

Now let's back up here, about two paragraphs OK. "Wasting the plenum", is going to affect the bacterial colonies in the "substrate" whatever that substrate is, Right? So, if you are not wasting continuosly, then the bacteria will have to recover after the "wasting" stops. Is this a fair statement?

Well I hope so, but at any rate, ANY FREQUENCY of wasting ( that is not continuous of course ) will cause a temporary effect to the bacteria colonies after the "wasting" stops, and "they" will then "recover".

It is the "depth" of this change in "oxygen gradient" and the trauma that the bacteria suffer as a result, that concerns me here, and I am particularly concerned actually, that the depth of oxygen gradient modification for very "infrequent" draws from the plenum, is going to really beat up on these bacteria colonies. Now you could reinnoculate with your favorite brand of bacteria or whatever, but I am just not seeing this as an advantage.

Now, of course, I am going to have to point out that high frequency wasting is not going to suffer as much from this "occasional" problem, and you might want to think or say, that at least "we" wouldn't have to suffer from this "all the time". Well let's just take a quick review, of post #14 ( or #15, if you want the short vesion ). Yeah, I know, but I am just not going to drip "2 more drops of blood" today, from my two fingers, over that one.

So at the "initial guestimate" of one pint, three times a day, on a 27 gal. tank, with 270 sq. in. of substrate, and a flow of 90 gph, for five seconds, WHE-E-W-W! Let's see. "We" are going to have a "downflow" of 7/64"across the entire water column area, again, three times a day.

Does this rate appear to anyone to be excessive in terms of "over-oxygenating" the substrate? Please let me know, as this is where I am conducting my "investigation" here, and investigaton is what this is ( to me at least )!

Now let's see; at 21/64" a day of "forced downflow" through the substrate, it is going to take 18 days for this oxygen to get to the bottom of the substrate ( if it is 6" deep ). This is going to "overoxygenate" the substrate?

Well, come on, educate me here. If that is going to happen, then I could go to once a day, for the one pint, and now we are at 54 days.


We were doing so good there for a while, but then "all of this".

Again, you are still working under the assumption that the 2-4mm substrate will remain static and undisturbed, which it won't.

I get what you are saying...sorry for asking for a re-post, exactly how deep do you plan on making your substrate here?

I thought I had covered that, but here goes; 3 to 4" of probably 2-4mm above the "plenum", then that 6mm "screen" to keep the ( particularly diturbing ) critters out, then the "playground" above that, at 3 to 4" additional of probably a 1 to 4mm "mix". It might be the "gobies" that "want" a finer grade than that ( to avoid gill damage ), but for now, 1mm minimum in the "upper layer" is the guess.

I agree 100%, it's a double edged sword...now the question becomes, which edge of the sword would you rather deal with? Inhibit detritus introduction and you also inhibit diffusion. Promote diffusion and you promote detritus introduction.

EX-ACT-A-MUN-DO! ! !

Ok...we want good diffusion, right? So let's deal with the detritus and waste....how about dealing with as much of it as we can mechanically BEFORE it becomes a problem in the substrate? With good flow, skimming, no overstocking/overfeeding, manual cleaning of the upper layers, ect...

EX-ACT-A-MUN-DO! ! ! . . . . AGAIN ! I just could not agree more!

Darn it!, I don't believe ( yet ) in mechanical cleaning of the substrate surface, or the upper layer, I let the crabs do that, and I do "by golly", have a little system currently, that does not have any detritus in it that you can see, and you can't find any in the top 3/4" of substrate either ( I gua-ran-tee that there is not any under that either )!

You can further check out my post in the current "algae control" thread as to where I stand on crabs and snails ( brittle stars could be excellent too, but with some reservations ).

I finally got the nitrate down under 1ppm, through a lot of patience ( careful feeding ) and not much else, other than the ( not wasting yet ) plenum. I still have a P problem, that I just found to be a tap water problem, and I will get that RO/DI unit "up and running", just as soon as "anything else" ( and it had better be soon! ). Let's dip that frozen food in the RO/DI while we're at it!

MikeS:
There is not going to be a winner here ( other than the reef keeping hobbyists ), and I am not striving for it. I do not think that you are either. I particularly share your concerns about "channeling" in the substrate, and just about everything else. I apparently think that I have a "little bit" of a handle on balanced flow in the plenum and the substrate, that I can offer help on, if and when anyone has interest in that subject.

> Wave98


OOps; the "detritus part"! Let's see if we can get into that in some subsequent posts, I certainly believe that it is a HUGE consideration.

Thanks again to MikeS in particular for his input.

Mojo Is also trying to track down some "diffusion models" for us to digest. Very important reading there, I expect!

Happy reef keeping!

 

[wave98]

Boy, I had a nice summary there too, but the forum says cut it down by 1,130 charachters, so OK.

I lost a good bit of it as well, but here is part of it.

I am actually deferring to both you and Mojo here currently regarding "diffusion" ( needs definition ), "advection"( which you pulled out of somewhere, but I understand it now ), chemical reactions that include P leaching ( one of my favorites ) etc., and then of course, I offer my expertise? in fluid mechanics, for whatever it is worth.

So let's not forget the "oxygen gradient", that we would like to have working for us here. I still believe that the "anoxic condition" that supports "faculative bacteria", along with the high and non aerobic "zones" are really the "crux" of what makes any of these systems work, along, of course, with all the other advantageous systems that we can "practicaly" bring to bear.

Funny thing here; The above, in this post, is really most of what I really wanted to say. the post above this one, I suppose, is "primarily" answering the questions that have been asked. Yeah, a little bit of reiteration there, but hey, if you have asked a question, and I have not answered it to your satisfaction, then ask it again, as you have, and thanks so much for doing so.

Such having been said, let's see if we can't get into some discussion of the things we don't understand well enough, as per above in this post. I sure could use some help here, and I can't possibly be the only one.

Thanks again! > . . Wave98

 

[MikeS]

I like the bugs and critters because they are interesting, and in many cases, they do help. I think that we should learn enough about these animals to pick the ones that help the most and try to avoid most of the ones that don't.

Agreed....it's an incredibly dynamic and unpredictable system, the less we rely on it the better (God, I'm starting to sound like one of those BB guys/gals... :doubt: :lol: )

Relying on them ( or anything else for that matter ), to the point of excluding other valuable "system maintainence" features, good husbandry or equipment, is likely ( along with poor husbandry in some cases ) to have been the cause of many failed systems and indeed much of the controversy that still abounds regarding substrate, refugiums, filtration, UV, charcoal, skimming, lighting; GEEZE! You name it!.

Agreed, every aspect of the system should be an attempt to compliment the system as a whole, no matter what it is...

Nice tank and creatures by the way! I particularly like your DIY "skimming intake" to the HOT filter. I've been threatening to make a similar modification to my "sea-clown" skimmer for the same purpose of gas exchange, as well as taking that crud directly to the skimmer. I see you've made some modifications to the skimmer and I'm particularly interested here, because the
adjustment on the "as purchased" skimmer $ucks, and I'm not happy about the micro bubbles either..

Thank you very much...I'd love to share the details of my modifications with you...

I'm curious too, about your carbon use as well. I agree with carbon use as well, although I'm a bit hesitant to run it 24/7. HEAVEN FORBID, that we should ( or not ) ever discuss Tri Based Carbon Pellets ( "TBCP" )!

Yeah, carbon is another topic I've seen batted back and forth over the years...and I've tried everything from no carbon, 50% of the time, 24/7 over the years as well :lol: Here's my basic take on it, the positives of carbon far outweigh the negatives...my tank does "better" with carbon 24/7 from a water quality standpoint. I'd be happy to elaborate more in another thread if you would like...

OOps! ! ! ! . . . . . No actually. It is the frequency and volume of "the draw", that will determine how the oxygen gradient is affected by "wasting".

Frequency and volume...actually that is exactly what I was saying...more frequency and more volume will generally equal more O2 in the substrate...agreed? You could likely figure out how much and how often to draw off to have some control over this, but as I've stated above, this will all be assuming a uniform, static substrate, which I just don't see happening long term. Channeling, water flow, rock placement, ect, ect, will make the substrate less uniform, therefore, when you draw off, some areas of the substrate will recieve very little diffusion, where others may recieve a lot. This unpredictable pattern makes it hard to determine how much O2 will reach the lower depths. You are in fluid mechaincs, so you know that water is going to generally follow the path of least resistance...say that path is in the hole that a burrowing fish has dug in the substrate...then the water diffuesd into the substrate at an unequal rate at that location, you may be introducing much more O2 (and detritus, ect) deeper into the substrate than you thought...get what I'm saying?

Firstly, it is my main endeavor here to learn enough about "Oxygen Gradation" to take an "educated estimate" as to how deep this oxygen gradient exists in a given substrate in a "normally static" ( unforced ) condition.

THEN, a person could take an "educated estimate" as to how this oxygen gradient might be affected by "wasting the plenum". The bacteria colonization is going to be affected by this "gradient", AND, modifying it by "wasting" is going to cause better or worse modification to occur in the bacterial colonies, and there are a lot of bacterial colonies "in there"!

I totally understand what you are saying, but again, you are basing all this on the substrate staying static and uniform over time, which it simply won't, for the various reasons I've outlined. That's one of the big problems I see with frequent wasting...

Darn it!, I don't believe ( yet ) in mechanical cleaning of the substrate surface, or the upper layer, I let the crabs do that, and I do "by golly", have a little system currently, that does not have any detritus in it that you can see, and you can't find any in the top 3/4" of substrate either ( I gua-ran-tee that there is not any under that either )

Ok, realize that crabs and other scavengers are but a single link in the chain, they consume waste, but they also produce it...by most estimates I have seen, even in a well balanced system, your crabs and such are only going to reduce total detritus amounts by maybe 15% or so...that leaves a lot of leftovers that must be dealt with by other means....the bulk of the nutrients still remain in the tank....

MikeS

 

[wave98]

Agreed....it's an incredibly dynamic and unpredictable system, the less we rely on it the better (God, I'm starting to sound like one of those BB guys/gals... )

You'll get over it! :lol:

Thank you very much...I'd love to share the details of my modifications with you...

...my tank does "better" with carbon 24/7 from a water quality standpoint. I'd be happy to elaborate more in another thread if you would like...

A PM, or another thread would work fine for either. "DIY Sea Clone Upgrade" maybe. There are probably still plenty of Sea Clone purchasers that haven't moved up yet, and are still "suffering". Thanks, I'd love it!

OOps! ! ! ! . . . . . No actually. It is the frequency and volume of "the draw", that will determine how the oxygen gradient is affected by "wasting".

Frequency and volume...actually that is exactly what I was saying...more frequency and more volume will generally equal more O2 in the substrate...agreed?

Well yes, exactly true! Frequency X volume = Oxygen Gradient modification.

You could likely figure out how much and how often to draw off to have some control over this,

And I have, It's that "pesky" post #14 again. That is not in the least "carved in stone" either by the way. Some effluent testing will tell us some here. So will time, and lot's of it ( unfortunately )

but as I've stated above, this will all be assuming a uniform, static substrate, . . . Channeling, water flow, rock placement, ect, ect, will make the substrate less uniform, therefore, when you draw off, some areas of the substrate will recieve very little diffusion, where others may recieve a lot.

Quite true again Mike, although I prefer "somewhat more and somewhat less". Rock placement and flow are "biggies" in any system IMO, and cannot be stressed enough!

This unpredictable pattern makes it hard to determine how much O2 will reach the lower depths. You are in fluid mechaincs, so you know that water is going to generally follow the path of least resistance...say that path is in the hole that a burrowing fish has dug in the substrate...then the water diffuesd into the substrate at an unequal rate at that location, you may be introducing much more O2 (and detritus, ect) deeper into the substrate than you thought...get what I'm saying?

Yes I do Mike, and I have all along, but I prefer "harder" in place of "hard", and I am "somewhat" less concerned with it than you are( maybe just a "little bit" less ). Further, you are exactly right again, about the burrowing fish, although I think that the fish is going to do a marvelous job of housekeeping, and at least I'm not so concerned about detritus entry here ( in his den ).

It is this fish, by the way, that is causing a lot of this "jumping through hoops" that it appears I may be doing here, and I will certianly admit that this is not making it easier. I am learning a lot in this attempt to solve that portion of "the problem" though.

In fact, in the 72" long tank that this is intended for, I may very well create a "gobies garden" or some such, in something like 1/4 ( or less ) of the tanks substrate area for this purpose, and use something more along the lines of your "approach" in the remainder. :idea:

Firstly, it is my main endeavor here to learn enough about "Oxygen Gradation" to take an "educated estimate" as to how deep this oxygen gradient exists in a given substrate in a "normally static" ( unforced ) condition.

THEN, a person could take an "educated estimate" as to how this oxygen gradient might be affected by "wasting the plenum". The bacteria colonization is going to be affected by this "gradient", AND, modifying it by "wasting" is going to cause better or worse modification to occur in the bacterial colonies, and there are a lot of bacterial colonies "in there"!

I totally understand what you are saying, but again, you are basing all this on the substrate staying static and uniform over time, which it simply won't, for the various reasons I've outlined. That's one of the big problems I see with frequent wasting...

Well OK, but it is not the "wasting", that is disturbing the substrate, at least not in the grain sizes that I have been considering, and I will continue to consider them until they don't need to be considered anymore. In fact, I have considered them a lot already, maybe more than you realize.

Ok, realize that crabs and other scavengers are but a single link in the chain, they consume waste, but they also produce it...by most estimates I have seen, even in a well balanced system, your crabs and such are only going to reduce total detritus amounts by maybe 15% or so...that leaves a lot of leftovers that must be dealt with by other means....the bulk of the nutrients still remain in the tank....

Exactly right again Mike, but it is in fact, a "net reduction" here, so they are not hurting the system in that regard. It isn't that reduction ( so much ) that I find them valuable for, however, but keeping the other "poop" up in the water column, for subsequent removal by mechanical and skimming, which they sure do a great job of in my tank.

And this occurs before the "poop" turns into real "detritus", and I see that as a huge benefit. You can have so many crabs in your tank, that it "looks" just about like "cooked rock", which unfortunately mine does! Some of them will die off eventually, I suppose, or I'll put some more of them into the refugium, once it is setup more appropriately.

I guess one of the points here is, that our tanks are not all going to be the same, and each one has to be tweaked to some degree, for each of us to get the most out of our little "chemistry set" here.

In summary, for MikeS in particular here, what we appear to have been disagreeing on, for the most part, is that "pesky upper layer", that I keep promoting, which could be evenly graded 2mm, for that matter, maybe 1/2" to 1" deep, something that the "burrowing critters" don't like as much ( and so off they go to their "garden" ), but which still helps with the detritus rejection that we would like to have, if we could just . . . .

Geeze, am I overly optimistic or what? :?:

Then there is that "darned" wasting" thing too, heh? So I explained in the previous post that it might take between 18 and 54 days for this "oxygen rich water" to get from the surface to the plenum depending on some currently arbitrary selection of 1 to 3 "draws" a day in a 6" (minimum ) substrate depth. So, how much oxygen does anyone think we might have in this water after 18 days of the bacteria populations working on it?

Yeah, OK, so maybe 9 days in some spots where the fish dug down to, but I did mention the "gobie garden" didn't I?

Thanks a lot Mike, I think we are starting to zero in on it some here, and it sure wouldn't mean much if we hadn't gotten some of the "whole system" concept considerations dealt with, along with debunking the "majic bullet" syndrome, that carves up so many attempts to make real progress in our reef keeping!

> Wave98

 

[tinman]

Great thread guys. Thanks for the invite wave.

I think you guys have covered all the basic thoughts and drawbacks I have seen in my own ideas for making a DSB system more productive for a long term answer. I, like you wave, kinda favor a way of layering. The twist I thought about adding to the layering was to use Crushed Coral over the manifold in the bottom 1" to hide the manifold and give easer pull for the manifold. Then a piece of screen over the top of that with a 6" fine grade sand layed on top. My thought that the CC would allow for a more even pull.

The question I haven't been able to get anywhere on is how much flow would it take to bring 1/4" of water through the sand? And would that be enough bottom change out to keep a stable level of areobic and nonareobic for the SB to still fufill its purpose?

Once agian great stuff guys. I will check back and add more of what I have toyed with when its not so late...

work comes early..

 

[wave98]

You're welcome Tinman, and welcome to RF!

I think you guys have covered all the basic thoughts and drawbacks I have seen in my own ideas for making a DSB system more productive for a long term answer. I, like you wave, kinda favor a way of layering. The twist I thought about adding to the layering was to use Crushed Coral over the manifold in the bottom 1" to hide the manifold and give easer pull for the manifold. Then a piece of screen over the top of that with a 6" fine grade sand layed on top. My thought that the CC would allow for a more even pull.

Well, you could try that, and it might work to some degree, but I'm concerned that 6" of "fine grain sand" is eventually going to promote "channeling". If, you can keep that 6" of "sand" at a fairly consistent depth like not less than 4" anywhere, it might be able to work, at least longer than otherwise.

I think you could go with 3-5mm at the "bottom" just as well, maybe better, but you might need another layer of 1-3mm vaguely ( for at least 1/2" to 1" ) above that to avoid "particle migration", much like MikeS has been concerned about here.

I don't think these oxygen processes are occuring all that deep in a "fine particle sand bed" however, except for anaerobic, and I don't think that is what we are trying to promote. Typical "sand beds" may be as deep as they are, just to extend the life of the "sink". Just my guess.

The question I haven't been able to get anywhere on is how much flow would it take to bring 1/4" of water through the sand? And would that be enough bottom change out to keep a stable level of areobic and nonareobic for the SB to still fufill its purpose?

Well, that is really the "crux" of this, the "oxygen levels" involved. We need more information, or just try it, and report back.

I'm looking for information on this, but it is hard to come by.

Let us know what you find. > Wave98

 

[MikeS]

Well, you could try that, and it might work to some degree, but I'm concerned that 6" of "fine grain sand" is eventually going to promote "channeling". If, you can keep that 6" of "sand" at a fairly consistent depth like not less than 4" anywhere, it might be able to work, at least longer than otherwise.

I think you could go with 3-5mm at the "bottom" just as well, maybe better, but you might need another layer of 1-3mm vaguely ( for at least 1/2" to 1" ) above that to avoid "particle migration", much like MikeS has been concerned about here.

Ok, I'm still trying to figure out what long term advandage layering the substrate with differing gradations of sand is going to give you. Sure, you may create a barrier for detritus introduction, but at the same time you are likely going to hinder diffusion in and out of the substrate, and several other negative secondary issues. I still say a uniform, coarse sand (2 or 3 to 4 or 5mm) is all you are going to need....

MikeS

 

[wave98]

Ok, I'm still trying to figure out what long term advandage layering the substrate with differing gradations of sand is going to give you. Sure, you may create a barrier for detritus introduction, but at the same time you are likely going to hinder diffusion in and out of the substrate, and several other negative secondary issues. I still say a uniform, coarse sand (2 or 3 to 4 or 5mm) is all you are going to need....

Well Mike, I hear you, but again:

You are looking at "wasting the plenum", fairly infrequently, like once every 3 mos. last I heard, so you are not going to "force" any "downflow" by "wasting", except for once every 3 mos..

I have some concerns about how that affects the health of the bacterial colonies in the substrate, but I expect they might recover in a few days or so, and that still might work out just fine, I don't really know.

I would still recommend wasting more often, for the sake of the bacteria, but I don't have any "hard evidence" on that either.

I have been promoting High Frequency Wasting, and that is a horse of another color. High flow, short duration, small volume "draws" can be more "evenly balanced" than otherwise, and flow, or diffusion if you like, can be "forced" through the entire "substrate area", including through the surface, whether it has smaller grain sizes or not.

I have not been promoting, thus far, any grain sizes smaller than 1mm, and larger grain sizes underneath are not going to block anything, except "particle migration", which I know that you are concerned about.

I have already answered that concern however, particle migration will not be a problem. If you would like to discuss that further, I would be happy to do so.

Thanks again > Wave98

 

[wave98]

It appears that interest in this thread is "waning". If no more interest is noted, then it will pass.

Thanks to all who contributed.

> Wave98