Plenums and the wasting "option"

[CaptiveReef]

Plenums and wasting

Plenums and wasting

The eggcrate incorperated might need to be looked at. If I understand what you are getting at captivereefing, you are saying that the space the eggcrate will create may be enough to reduce the risk of o2 getting into the anaerobic zones we want to keep in the lower layers of the "Substarte"

Have you tried this? Very interesting. any reading on that?

Yes you got! It would be a more controlled environment by having that space. I have experimented with this when I designed a filtration system to raise larval marine fish. I needed a way to filter a tank without any danger of sucking up the fish, but still be able to maintain full spectrum filtration.
Here is a drawing of the tank design and I will be posting an operating one shortly.

CaptiveReef

 

[barryhc]

God you're good Kris! That is however where we are at, and I think that there is some information out there on this as well.

I've read some, but only opinions so far, not something more concrete. If you take a peek at my last post to CaptiveReef, you will see that I made some speculation about this.

There may in fact, be some very good information on this.

I may not be right, but I continue to speculate, that a good portion of many sand bed depths, actually do "sink" a lot of conmpounds, and they eventually become a problem in some cases, usually over a long period of time.

So let's just throw out some of that lower stuff, and enjoy it, heh?

Let's be careful while we are doing it, that we keep our flow balanced, draw short distances so we don't kill the bacteria, and do it on a regular basis, so our reef is "stable".

Thanks > barryhc

 

[barryhc]

Nice diagram CaptiveReef. It makes a lot of sense to me. That is just what I have been proposing, except for feeding it continuously to a skimmer.

Where is your design at now?

Thanks for the info. > barryhc

 

[CaptiveReef]

Plenums and wasting

Plenums and wasting

After that, however, I'm getting lost here, as to what the advantage is going to be from "drawing " from the middle of the substrate depth. I see how it evens the flow for you, and avoids some portion of the potential channeling problem, but, I just don't understand how you get bacteria down to the bottom of the bed, if you are "pulling from the middle".


Thanks again > barryhc [/B][/QUOTE]
The natural diffusion will bring the waste to the egg crate level, then you are able to draw from it from below, having this egg crate space will make it easier to collect the waste for the draw and protect the upper levels from having to much oxygen drawn in. You can now have a draw level, and a functioning DSB or Plenum.

CaptiveReef

 

[CaptiveReef]

Plenums and wasting

Plenums and wasting

Nice diagram CaptiveReef. It makes a lot of sense to me. That is just what I have been proposing, except for feeding it continuously to a skimmer.

Where is your design at now?

Thanks for the info. > barryhc

I have all the materials, I'm actually going to add water this weekend. I'll post pics of this project while it's under construction.

CaptiveReef

 

[barryhc]

I installed one of these in my 27 gal. hex tank 4 months ago.

I have not started "wasting" yet.

I still am curious if you intend to feed the "efflurnt" to the skimmer.

> barryhc

 

[CaptiveReef]

filter design

filter design

I installed one of these in my 27 gal. hex tank 4 months ago.

I have not started "wasting" yet.

I still am curious if you intend to feed the "efflurnt" to the skimmer.

> barryhc

The water from the bed 1st goes through the skmmer then it goes into the power filter, on the other side of the skimmer is an elbow to direct the skimmate into a hanging cup, the power filter does all the drawing.I have to use a small power filter because you are limited to how fast the water is able to go through the substrate. Also dealing with larval marine fish and inverts, they are pretty much floating blobs until they morph into something a little more solid, so gentle water movement is what I'm looking for.


CaptiveReef

 

[kbmdale]

Here is a decent read with some of the same principles we are trying to apply..

http://www.reeffrontiers.com/forums/archive/index.php/t-2931.html

Barry you might have already read it.

 

[haid]

I have also been thinking about some of this. What I was thinking however would be to get some flow without oxygen into the bottom plenum, thus doing your mixing. Then use a metering pump to continuously draw water from the plenum. This should stabablize any rapid changes in the bacteria levels. I was trying to come up with a good way to seperate the anoxic layer and the aerobic layer. I was thinking something along the lines of what a reverse undergravel filter would do. Use some real fine sand above the plenum (to house the aneroxic) then have a space of some sort (maybe manifold/undergravel here) then a larger grain size for the top layer. Continually wasting from the plenum and occasionally back flushing the top larger grain substrate. This should leave the aneroxic layer alone while allowing a lot of detritus to be pushed from the larger grain anerobic layer above. The skimmer could then remove what is pushed into the water column. Just what I have been thinking.

 

[barryhc]

By CaptiveReef:

The water from the bed 1st goes through the skmmer then it goes into the power filter, on the other side of the skimmer is an elbow to direct the skimmate into a hanging cup, the power filter does all the drawing.I have to use a small power filter because you are limited to how fast the water is able to go through the substrate. Also dealing with larval marine fish and inverts, they are pretty much floating blobs until they morph into something a little more solid, so gentle water movement is what I'm looking for.

So flow through the substrate is equal to the "outflow" of the power filter?

This flow is "continuous"?

Is this affecting the oxygen level in the "substrate"?

Thanks again. > barryhc

 

[CaptiveReef]

By CaptiveReef:



If we move the "entire water column" down, from the top of the water, to the glass at the bottom of the tank, and the distance we move this water is, say, 1/8", and that is 1 pint of water, and it takes about 5 seconds, and then we leave it alone for 8 hours, what is the effect going to be on the bacteria?

I have to start here. > barryhc

The area we are really concerned with is the top layer of the DSB or Plenum, that pint of water can be constantly moved from the water column to the top of the bed at a rapid rate,( the normal flow a powerhead would create), but it's the rate it goes through the bed, a 5 second draw through the bed would destroy the environment for the bacteria, the 8 hours after would not even matter with that pint of water. There has to be natural diffusion in the bed up to that eggcrate level, then a 5 second draw can be made without effecting the upper levels.

CaptiveReef

 

[barryhc]

Yes Kris, I read all of it. Did you notice that the thread "died" in Nov. of 2004?

Everyone got "bogged down" in "detritus removal" and nothing got tried or reported on.

I can handle detritus removal at the surface pretty easily, so that thread just wasn't offering anything for me.

They never really adressed the issue of maintaining an advantageous "oxygen gradation" in the substrate, or what particle size, bed depth, flow rate, layering, frequency or volume of "draw", etc.

Oh well. > barryhc

 

[CaptiveReef]

By CaptiveReef:



So flow through the substrate is equal to the "outflow" of the power filter?

This flow is "continuous"?

Is this affecting the oxygen level in the "substrate"?

Thanks again. > barryhc

Yes the flow is equal and continuous, I'm using the substrate as a pre-filter, there is a divider wall that has a DSB on the other side. Using a very small under rated powerfilter I'm able to create the constant draw through the substate, then directly into the skimmer then into the powerfilter, back into the tank.


CaptiveReef

 

[barryhc]

By haid:

I have also been thinking about some of this. What I was thinking however would be to get some flow without oxygen into the bottom plenum, thus doing your mixing. Then use a metering pump to continuously draw water from the plenum. This should stabablize any rapid changes in the bacteria levels. I was trying to come up with a good way to seperate the anoxic layer and the aerobic layer. I was thinking something along the lines of what a reverse undergravel filter would do. Use some real fine sand above the plenum (to house the aneroxic) then have a space of some sort (maybe manifold/undergravel here) then a larger grain size for the top layer. Continually wasting from the plenum and occasionally back flushing the top larger grain substrate. This should leave the aneroxic layer alone while allowing a lot of detritus to be pushed from the larger grain anerobic layer above. The skimmer could then remove what is pushed into the water column. Just what I have been thinking.

Haid, I think your starting to get into my particular area of interest here, by discussing the "oxygen levels" ( or gradations ), in the substrate.

However, I think the term "Aneroxic" is exceedingly dangerous!

Aerobic > Lots of oxygen > maybe up to 80% saturation near the substrate surface.

Anoxic > Not very much oxygen > I haven't seen any good definitions.

Anaerobic > Devoid of oxygen.

These terms, Anoxic and Anaerobic, get thrown around a lot, but it is really hard to tell, a lot of the time, what the person using the term, might actually mean by it. Seriously!

The "Goemans and Gamble" cdrom, "New Wave" makes a careful distinction of these terms, and it is an interesting read. It is "Ungodly" lengthy, and I don't necessarily subscribe to many of the Proposals made in that 'Ebook".

You might actually be making a good point here, but I have to point out the distinction of these terms, before I can consider it more seriously.

I'm hoping you might have meant "Anaerobic".

Did I get lucky? > barryhc

 

[barryhc]

By haid"

Continually wasting from the plenum and occasionally back flushing the top larger grain substrate.

I believe that any kind of "true continuous wasting" causes a mechanical "nightmare" for "flow balancing".

Read the thread from the beginning if you want a more thorugh explanation of flow balancing, and why "short duration draws" will keep "downflow distances" within a range, that the bacterial populations can thrive in, instead of "suffer from"!

Nice to have you here. Thanks > barryhc

 

[haid]

barryhc,


Yes, Anaerobic is what I meant. Sorry not always great with terminology. I would think this method would allow you to keep the top layers from going anaerobic(pushing water up and through from the column), reduce the load on the sandbed to begin with, with less large particles there to break down. The phosphate should migrate most of the time to the bottom plenum and be wasted in a slow continuous manner. In effect draining water for small but continuous water changes.

 

[barryhc]

Well, "haid", that's pretty interesting, actually, It is sort of the opposite of what I am trying to do, and that could be closer than people think.

I'm just going to post his now, because usually, "we" end up trying to type fast enough to keep the posts "in order ", and that often causes the posts to "cross" in transmission, and seems pretty "odd" to many of us when we read them!


Thanks again. > barryhc

 

[barryhc]

By CaptiveReef:

The area we are really concerned with is the top layer of the DSB or Plenum, that pint of water can be constantly moved from the water column to the top of the bed at a rapid rate,( the normal flow a powerhead would create), but it's the rate it goes through the bed, a 5 second draw through the bed would destroy the environment for the bacteria, the 8 hours after would not even matter with that pint of water. There has to be natural diffusion in the bed up to that eggcrate level, then a 5 second draw can be made without effecting the upper levels.

Why is it the "top layer" that we are concerned with, and just how deep is this top layer?

The 5 second "draw" is a "sub function" of "draw depth". It is not the important factor here.

The "draw depth" is the important factor, at least in my opinion, and it is of course, only an opinion, but we could make the "duration" of the "draw" 1/2 second if you like, or 30 seconds, but it is the depth of this draw, that will most affect the bacteria.

"Draw depth" is the distance you "pull" water down into the substrate each time you "draw" through the plenum.

If this "depth" is that crucial, we could reduce that depth to, say, 1/32" each time.

You are headed in a slightly different direction here, than I am,
and I don't have any problem with that, but I don't think the bacteria really care.

If the bacteria population is going to be destroyed by drawing water into the substrate 1/8 " at a time, then I would like to hear some explanation as to why, or how, that is so.

I'm not even disputing it, yet.

Thanks again, > barryhc

 

[barryhc]

By "haid":

Yes, Anaerobic is what I meant. Sorry not always great with terminology. I would think this method would allow you to keep the top layers from going anaerobic(pushing water up and through from the column), reduce the load on the sandbed to begin with, with less large particles there to break down. The phosphate should migrate most of the time to the bottom plenum and be wasted in a slow continuous manner. In effect draining water for small but continuous water changes.

Well, I agree with most of this actually, if I'm reading it right.

I don't think though, that we have any concern, or problem, so much, with the "upper level" ( or layer ) "going Anaerobic", but how deep, or thick, is this "upper layer" anyway?

Especially, if "we" are "forcing" water to flow down into the substrate very often, for very "short distances"? This will keep the "upper layer" Aerobic, right?

I do not believe that this would over "oxygenate" the "depths" of a 6"- 8" deep substrate. This would be at the rate of about 5/16" of downflow, per day. It would take 20 days for this water to reach the top of the plenum. This rate, is going to destroy the bacteria?

I am actually looking for "critters", crabs in particular, to keep the surface of the substrate rather clean, and high flow, as well, to keep this "stuff" in "suspension", for removal by skimming etc..

Substrate in the 1-2mm range will "reject" a very large portion of any detritus that "wants" to collect at the surface, and crabs, and high flow, would get "it" into the water column.

This portion of the detritus control consideration is working very well, in my tank, and has been for more than 7 mos.. I know that isn't all that long, but I would have noticed a detritus problem by now, wouldn't I?

Anything "continous" has a lot of associated "flow balancing" problems, if the flow is going to be "wasted".

Let me know what you think here "haid", and Thanks. > barryhc

 

[CaptiveReef]

Plenums and wasting

Plenums and wasting

By CaptiveReef:


Why is it the "top layer" that we are concerned with, and just how deep is this top layer?

The 5 second "draw" is a "sub function" of "draw depth". It is not the important factor here.

The "draw depth" is the important factor, at least in my opinion, and it is of course, only an opinion, but we could make the "duration" of the "draw" 1/2 second if you like, or 30 seconds, but it is the depth of this draw, that will most affect the bacteria.

"Draw depth" is the distance you "pull" water down into the substrate each time you "draw" through the plenum.

If this "depth" is that crucial, we could reduce that depth to, say, 1/32" each time.

You are headed in a slightly different direction here, than I am,
and I don't have any problem with that, but I don't think the bacteria really care.

If the bacteria population is going to be destroyed by drawing water into the substrate 1/8 " at a time, then I would like to hear some explanation as to why, or how, that is so.

I'm not even disputing it, yet.

Thanks again, > barryhc

In this theory the upper layer of substrate is the deeper portion of this bed. The bottom layer is sharing space with the manifold most of the draw point will be around the manifold and just above it. With the 5 second draw these low area's will be only affected, the upper depth of the bed will not be affected so oxygen will not be pulled into the bed.
This way diffusion will be performed naturally in the upper bed, and the waste that has been diffused down to the manifold area can be drawn out.
You are looking to manually draw the water 1/8 inch at a time through the bed, you would have to draw the water from an uplift tube, like you said a pint at a time every 8 hours.
The only problem I see with this is 8hrs enough time for the bacteria to break down the Nitrate into Nitrogen before the next draw.
You are going to have to build a prototype and try it, if you have a rise in Nitrates then the process is compromising the DSB.


CaptiveReef