Plenums and the wasting "option"

[haid]

Another off the wall option to just throw out there I was thinking about is creating a false anoxic layer. We should easily be able to blow out the aerobic layer on top(reverse undergravel). So that gets us to Nitrate and left over phosphate, ect. What I was thinking is create the plenum base with not sand but a partition(glass, acyrlic). With the Aerobic section/liverock puting nitrate back to the system water along with unbroken down detritus. Ok now the plenum is kept oxygen difecient with the use of the partition and a slow draw from the plenum. Ok so you barry coils of tubing in the top aerobic layer and hook them to small bulkheads through the partition. The slow draw from the plenum will cause new flow to the plenum. The coiled tubing becomes the anoxic layer. Thus Breaking down the nitrate. Phosphate remains but is removed by the continuous wasting from the powerhead mixed plenum. Maybe too complicated to work right. Not sure but I think this could leave a nice "sand bed" for looks on top that will not be "loaded" and could be used by critters. Should eliminate pluging and problems with diffusion rate to the plenum. And a continuous wasting of the "sink". Also the use of wet skimming/good flow to remove what is pushed up and out of the top aerobic layers and to reduce settling on rocks. And also as mention before slow but constant water changes that should not effect oxygen levels in any of the zones and would keep them from shifting to different depths over time. I have a 55 gallon that I am thinking of trying to run simular.

 

[kbmdale]

Re: Diffusion

Re: Diffusion

Yes to make the area bigger it would have to be not deeper, but larger over an area, (square footage) A tank that is greater in depth(front to back) would have a better anoxic area than a tall tank.



CaptiveReef

so that brings upmy next point, would a 18-24" wide tank be better than a 12" wide tank for this set-up?

I am also putting together a 16x16x16 cube for a softy tank.

 

[barryhc]

By Kbmdale:

so that brings upmy next point, would a 18-24" wide tank be better than a 12" wide tank for this set-up?

It depends on the tank "height". The "length" of the tank is unimportant, it is the "width", or dimension from front to back that counts.

Actually, It is the ratio of height to width that gives you a larger surface area, relative to the water volume.

Anyway, the 16 X 16 is a good ratio, lots of area compared to the water volume. It also helps with lighting requirements as well, making T5's a more reasonable posssibility, if you wanted to go that way. I'm not promoting T5's, they just work better in shallower tanks.

Sounds pretty good. Substrate, in the "softy tank? > barryhc

 

[kbmdale]

Undecided on size of substrate yet, THe only guarentee, you won't see any acrylic on the bottom...lol....

 

[barryhc]

I don't wear pink, and my tank has a glass bottom on it! :lol:

It has some arag. gravel, sand, and CC on it too!

I'm going to be using some acrylic for my "fuge". . . Maybe just sand over there though. How deep should it be?

> barryhc

 

[kbmdale]

The best fuge I ever ran was built like this

8" sand bed
water goes in and dropps any detritus it might bring with it in the left chamber, then moves swiftly across the top of the sand and over into the return chamber. You can vacuum the first and last chambers and be detritus free,

 

[barryhc]

So Kris, did you "catch" any of that stuff about "particle migration", "plenum clogging", Anoxic and Anaerobic bacteria populations in the "lower level" of substrate?

Maybe were back to the mechanical portion, of the "flow design". Your original diagram was actually pretty good, LOTS of holes there. Gotta consider "flow restriction" here, we actually WANT some flow restriction based on the "total area" of these holes, in order to maintain fairly even "flow balancing".

Good luck with the "softy tank", > barryhc

 

[barryhc]

Kris, did you keep any algae, Micro, or Macro in that refugium design?

> barryhc

 

[kbmdale]

Kris, did you keep any algae, Micro, or Macro in that refugium design?

> barryhc

Nope I had a seperate aglae grow out tank. I found the macro liked higher flow than my DSB could process... Th fuge above only had about 150 gph rolling through it, seems the DSB needed the slower flow to filter the water. MY macro's loved 600-800 gph tubling them.... But this was way off the topic so back to the lecture at hand

 

[kbmdale]

So Kris, did you "catch" any of that stuff about "particle migration", "plenum clogging", Anoxic and Anaerobic bacteria populations in the "lower level" of substrate?

Got it...or a good enough understanding of what we need it to do.

Maybe were back to the mechanical portion, of the "flow design". Your original diagram was actually pretty good, LOTS of holes there. Gotta consider "flow restriction" here, we actually WANT some flow restriction based on the "total area" of these holes, in order to maintain fairly even "flow balancing".

Yep this is the step I see next. We need an even pull manifold that allso has a backward bump for time to time to unclogg.

 

[barryhc]

I guess you're right. :lol: I have to run, Enjoy! > barryhc

 

[barryhc]

EXACTAMUNDO!! BYE! > tomorrow > barryhc

 

[kbmdale]

chech your PM

 

[CaptiveReef]

Plenums and Wasting

Plenums and Wasting

By CaptiveReef:


>>Are you still suggesting to "draw" from somewhere in the "mid-level" of the substrate depth? Is that putting the "manifold" above a 2" thick "lower bed", and under a 4" thick "upper bed"?<bhc>

By CaptiveReef:


>> I imagine those depths would work pretty well, for a "regular DSB".

Did you catch the part about "particle migration" and not "plugging up" the plenum?

Just checking. > barryhc

Yes I got the part about particle migration, I have been thinking about the manifold placement with both setups.
What I'm suggesting is have the manifold in the 2'' bed on the bottom with a DSB setup, and have the manifold in the empty Plenum space with the Plenum setup. I feel with the Plenum setup, it would function alot better due to the manifold is open and it would be a better draw. Also with the Plenum application you may be able to get a longer draw because it is at the very bottom of the bed, which would make a better draw on the lower zone of the bed.




CaptiveReef

 

[voodoody]

I guess I don't understand the concern with flushing the anoxic and anaerobic layers with "clean oxygenated water". Understand that oxygen is not toxic to anaerobic bacteria, these bacteria simply do not require oxygen for their metabolic processess. The anaerobic bacteria will exist on a biofilm. It would be highly unlikely that their populations would decline with an intermittant fast flush. The oxygen would likely be consumed quickly via diffusion into the upper bed and the anaerobes would soon be functioning as usual. I do agree that if this was done on a continual basis with large volumes, the bacterial flora of the deeper layers could be changed. This, however, is not required to flush the lower layer nutrient sink periodically.

 

[CaptiveReef]

Plenums and wasting

Plenums and wasting

I guess I don't understand the concern with flushing the anoxic and anaerobic layers with "clean oxygenated water". Understand that oxygen is not toxic to anaerobic bacteria, these bacteria simply do not require oxygen for their metabolic processess. The anaerobic bacteria will exist on a biofilm. It would be highly unlikely that their populations would decline with an intermittant fast flush. The oxygen would likely be consumed quickly via diffusion into the upper bed and the anaerobes would soon be functioning as usual. I do agree that if this was done on a continual basis with large volumes, the bacterial flora of the deeper layers could be changed. This, however, is not required to flush the lower layer nutrient sink periodically.

If you introduce oxygenated water into the bed, you will remove any Nitrate, which is a usable source for the bacteria. They use the Nitrate to breathe. Also the environment that is created in the bed in which these bacteria need to perform their function will be disrupted, and the end product will be Nitrate levels spiking.
In this discussion we are trying to do small timed draws of water to remove waste that has diffused to the bottom of the DSB bed or Plenum, without introducing oxygenated water into the bed in the same process.

CaptiveReef

 

[salty joe]

This thread is very interesting.

I have also been kicking around the idea of regularly draining a sand bed. What I am considering is a deep sand bed with a plenum underneath. I would have a single drain in the bottom of the tank. I would probably place a layer of window screen about an inch or so from the bottom of the sand to prevent animals from digging clear to the plenum in an effort to minimize channeling. At the drain I would place a one-inch shutoff valve (top valve). From there I would run a pipe straight to the floor, and with 2 90Ã"šÃ‚° elbows turn the pipe straight up so that it was higher than the highest point in my aquarium. At the bottom of this U tube, I would place another shutoff valve. To drain the plenum, I would make sure the bottom valve is closed and open the top valve. The water in the U tube would then reach the same level as the water in the aquarium. Then, I would close the top valve and open the bottom valve to empty the U tube. This way, the amount that I remove would be consistent each time. I could construct the U tube from different sizes of PVC to adjust how much water I remove. No moving parts to fail.

I would monitor the phosphate in the water that is exported from the plenum. In my opinion, the system would be dialed in when the phosphate level in the exported water is steady week after week and the tank is doing well. To me, this would indicate a balance has been struck between how much phosphate is going into the sand bed and how much phosphate is being exported from the sand bed. Incidentally, I also think that perhaps phosphate measurement from the plenum water would be an indirect measurement of other undesirable things like metals and who knows what else.

With this system, I wouldn't care if it took five minutes or five hours to fill the U tube. I am also not too terribly concerned about channeling. As long as phosphate exports were consistent, and the aquarium was doing well, I would feel comfortable.

The one thing that I am not sure about is what kind of membrane should I use for the very bottom of the sand bed to keep the very fine sand out of the plenum?

Just my thoughts on the matter. I look forward to watching this thread grow.

Joe

 

[barryhc]

By voodoody:

I guess I don't understand the concern with flushing the anoxic and anaerobic layers with "clean oxygenated water". Understand that oxygen is not toxic to anaerobic bacteria, these bacteria simply do not require oxygen for their metabolic processess. The anaerobic bacteria will exist on a biofilm. It would be highly unlikely that their populations would decline with an intermittant fast flush.

>>This information could be helpful, It is the kind of information that I have been looking for. Please give links, or otherwise, to "back it up". and Thanks! <bhc>

My take on it, (without "better information" ) is that Anaerobic bacteria "predominate" in an Anaerobic area. "They" either" migrate or develop there. They "like it there". They have food there and they are alive there. If a "significant"change in the oxygen level occurs there, other bacteria that like the new level of oxygen, will migrate there. Now we have fostered some competition in this area between bacteria colonies. Is this good or bad? <bhc>

By voodoody:

The oxygen would likely be consumed quickly via diffusion into the upper bed and the anaerobes would soon be functioning as usual. I do agree that if this was done on a continual basis with large volumes, the bacterial flora of the deeper layers could be changed. This, however, is not required to flush the lower layer nutrient sink periodically.

>>There's that "diffusion" word again. I thought "we" agreed, that diffusion had to do with downward motion, that occurs as a direct result of nitrogen gas bubbling up, and therefore pulling water downward. "Oxygen consumed via diffusion"?

Shall "we" define "diffusion again? > CaptiveReefs' department.

"Flush HOW MUCH"? Say, 2" of "water column"? 1/4"? <bhc>

Nice post, and welcome "voodoody", I'm just asking questions. > barryhc

 

[voodoody]

Oxygen will be consumed by aerobic bacteria in the upper sand bed. As this happens, oxygen will diffuse from the flushed lower sand bed to the upper bed. The rate of diffusion is the only variable. If the diffusion takes an eternity, it might allow for replacement of the bacterial flora with an aerobic species until the oxygen is used again. I do not have anything to back it up, however, it is intuitive that the rate of diffusion of a gas to the upper sand bed will be quicker than the downward repopulation/replacement of anaerobes by aerobes in the lower sand bed. Again, this might be different if oxygen were actually toxic to anaerobes, however, it is not. I have a plenum in my DSB modeled after ldrhawke with some variations. I did use a "packed grid" with very small holes to prevent "short circuiting". I used the same substrate. I did not use a fabric barrier as he did as I felt it would trap the sand critters.

I wouldn't hesitate to flush any volume of water through the bed. I think you could flush an equivalent volume of the whole sand bed or more and within a few days, the anaerobic zones will be functional. I have no "proof" of this yet, but I do have an understanding of how bacterial flora survives even short term antibiotic therapy if a biofilm has been established. My tank has only been set up for 3-4 months, however, and I have not flushed yet as I do not think significant nutrient loads are present. I did flush several times before placement of the bed to verify the function and speed of the flushing action. It is amazing how fast water can drain through numerous tiny holes.

 

[barryhc]

By CaptiveReef:

Well I'll try to tackle the ol diffusion discussion without making a fool out of myself, (I hope). As we know diffusion occurs in the DSB where the perfect conditions are present to create an anoxic zone. The actual diffusion is when the bacteria in the anoxic zone use the NO3 to breathe they strip away the oxygen molecule and leave one Nitrogen atom to bubble up as Nitrogen gas. The process of the slow release of Nitrogen bubbles and the introduction of new water into the bed when the Nitrogen is released is the diffusion process.
Hope I got this one?

>>CaptiveReefs' definition of diffusion was accepted as stated, and I still accept it.

Still, after the Anoxic bacteria strip the oxygen molocule from NO3, and then bubble up Nitrogen gas, what is left from that process, besides the bacteria? No dispute here, but do you have a link for this? I love to read.<bhc>

By CaptiveReef:

If you introduce oxygenated water into the bed, you will remove any Nitrate, which is a usable source for the bacteria. They use the Nitrate to breathe. Also the environment that is created in the bed in which these bacteria need to perform their function will be disrupted, and the end product will be Nitrate levels spiking.

>>OK, I'm getting confused here, and I rarely get confused.

I thought we wanted to remove the Nitrate in the Anoxic zone, and so, if "we" add oxygen, we will "remove the Nitrate"?, and we are going to get a "Nitrate spike"?

Help!! where's that "reading" on this, now my head hurts too!

Thanks again, >"reading, links" > barryhc