Plenum or Insanity?

[florida joe]

As I get ready to put together my Refug I still have thoughts about a plenum. Does this make any sense to anyone other then me? The substraight is a major contributor to biological filtration. Predicated on its depth and the amount of oxygen available. At the substraight bed surface we get nitrification and deeper in the substraight oxygen decreases to the point where we get denitrification. With out it we would not be able to sustain our aquariums.
My thinking now is this. If I make a support out of PVC pipe place some plastic screening over it so it allows the dissolved compounds to diffuse between the gravel substraight and the plenum.
The plenum now provides a layer of water below the substraight that would maintain a level of dissolved oxygen above zero. Hydrogen sulfide which inhibits bio filtration can form in any thick sand bed but by sandwiching the substraight between two oxygenated zones I would greatly reduce this if not eliminate it all together I think I am in fact getting the benefit of two pronged filtration. I would still have regions within my substraight were the oxygen level is near zero and this is where denitrification will occur as well as with in my live rock and algae.
Are these just the rantings of a lunatic mind or do I make some sort of sense to anyone

 

[scopus tang]

Boy Joe, I got to tell you lost me here. I researched plenums quite a bit back when I first got into this hobby, and everything I could find on them at the time stated that there was no documentable benefit of having a plenum over a DSB. Now they may very well have come out with something in the meantime, cause I really haven't been paying much attention. I could be wrong, But I kind of thought that plenums had kind of faded out of popularity. Based on what you described, my question would be, how will you get oxygen to the bottom of your sandbed (i.e. under the plenum) if there is layer above which is aneorobic? That aneorobic layer will prevent any oxygen from going deeper in the bed. Or am I misunderstanding your set-up?

 

[florida joe]

My friend it is people like you that I love question, question, and question some more it shows me you are at least thinking about my thread. A cleaning crew would keep my substraight oxygenated I in fact had the same question how do I maintain oxygen in the area below my plenum and this is what I was lead to believe by experts on the field.
The oxygen is likely produced by partial brake down of nitrate so the dinitrifing would also produce oxygen but it may be a byproduct of other reactions with in the deeper layers of the sand bed These reactions involve the breakdown of organic matter both dissolved and particulate, a food source for some of the bacteria that converts nitrate to nitrogen gas. Oxygen at levels above zero has been recorded 100 % of the time they were taken from the water below a plenum. On this I must defer to what the experts say .

 

[scopus tang]

Originally Posted by florida joe
http:///forum/post/2569945
My friend it is people like you that I love question, question, and question some more it shows me you are at least thinking about my thread. A cleaning crew would keep my substraight oxygenated I in fact had the same question how do I maintain oxygen in the area below my plenum and this is what I was lead to believe by experts on the field.
The oxygen is likely produced by partial brake down of nitrate so the dinitrifing would also produce oxygen but it may be a byproduct of other reactions with in the deeper layers of the sand bed These reactions involve the breakdown of organic matter both dissolved and particulate, a food source for some of the bacteria that converts nitrate to nitrogen gas. Oxygen at levels above zero has been recorded 100 % of the time they were taken from the water below a plenum. On this I must defer to what the experts say .
Alright, your oxygenating your upper layer with a cuc, and relying on the denitrification process to provide oxygen to the water below the plenum. It seems to me then, that your DSB would have to be a minimum of 6" deep in order to provide a midlayer in which you would have a oxygen level near zero. Now explain to me how the presence of oxygen is going to break down hydrogen sulfide gas (obviously I'm no chemist)? And more importantly why is it of concern? Also beyond removing the gas, what are you hoping to accomplish with the plenum? The reason I ask, is because I've been running modified DSB in my tanks for about 5 years now, and I've never had an issue ~ so I'm curious as to what it is you are trying to accomplish, as well as what issues you are concerned with.

 

[tizzo]

Is the plenum for the fuge or for your DT?
The reason I never went with one is because I didn't want something as simple as a fallen rock to disrupt the parameters of my tank. Just not worth it IMO, but if your doing it in the fuge then I think it would be safe. Redundant? Maybe...

 

[florida joe]

Originally Posted by Scopus Tang
http:///forum/post/2569972
Alright, your oxygenating your upper layer with a cuc, and relying on the denitrification process to provide oxygen to the water below the plenum. It seems to me then, that your DSB would have to be a minimum of 6" deep in order to provide a midlayer in which you would have a oxygen level near zero. Now explain to me how the presence of oxygen is going to break down hydrogen sulfide gas (obviously I'm no chemist)? And more importantly why is it of concern? Also beyond removing the gas, what are you hoping to accomplish with the plenum? The reason I ask, is because I've been running modified DSB in my tanks for about 5 years now, and I've never had an issue ~ so I'm curious as to what it is you are trying to accomplish, as well as what issues you are concerned with.
The depth of my sand bed really is not an issue in so much as I can have pockets of near zero oxygen in as little as one inch of substraight. I was thinking on the lines of 4 inches
As I am sure you know hydrogen sulfide often results from the bacterial break down of organic matter in the absence of oxygen, so the more oxigenated my substraight the less chance of having it. the rapped relese of it can kill fish quickly.It also inhibits bio filtration
The majority of my dinitrificaton hopfully will take place in my DT as well as the alge I will grow in my refug. As far as what I am trying to accomlist. Its as much bang for my buck I can get as long as I am going with a refug I would like to squeese as much good out of it as I can. I fell that in my 4inch sand bed turning it into two two inch onces with in the same space will give me over all more benifet.
Above all I by no means say this is a blue print for a refug. I started this thread to get in put and I thank you for yours

 

[florida joe]

Originally Posted by Tizzo
http:///forum/post/2570197
Is the plenum for the fuge or for your DT?
The reason I never went with one is because I didn't want something as simple as a fallen rock to disrupt the parameters of my tank. Just not worth it IMO, but if your doing it in the fuge then I think it would be safe. Redundant? Maybe...

It will be in my refug I don’t know if it’s so much redundancy as expansion

 

[scopus tang]

Ok Joe, you made me go dig out the books; I'd blame you for making me burn the midnight oil as well, but I'm afraid other issues contributed to that. So, here is what I found for you; taken from Natural Reef Aquariums by John H. Tullock (excellent resource, and I highly recommend it, if you don't already have it)
"The notion of having a plenum with a layer of "dead" water at the bottom of the aquarium strikes some hobbyists as either unnatural or too complicated. A number of Americans have modified the Jaubert method simply by adding a layer of live sand several inches deep to reef aqaurium already containing significant amounts of live rock . . . In exchanges on internet aquarists' forums, others have reported similar success without the use of a plenum, but some hobbyists have also experienced the developments of pockets of hydrogen sulfide gas in live sand bed that do not have the benefit of a plenum. Jaubert and others suggest that the plenum allows a very slow diffusion of water and gas through the sand, thus avoiding noticeable hydrogen sulfide problems."
It appears that your theory is in fact supported by the experts; I would point out however somethings in regards to Jaubert's system;
Layer #1; egg crate or a regular undergravel filter supported about 1" off the bottom of the tank, covered with plastic or fiberglass screen.
Layer #2; a 1 to 2 inch deep layer of silica sand, crushed coral, or other materials that will not readily dissolve. Aragonite should not be used for this layer, or it may eventually turn into a chunk of "concrete."
Layer #3; a second layer of screening is placed atop the first sand bed. On top of this another 1 to 2 inches of substrate is placed. This looks and works best if composed of aragonite, live sand from the ocean, crushed coral and crushed shell fragments, with about half the total amount being aragonite and/or live sand.
Since your major concern appears to the accumulation of Hydrogen sulfide gas, while trying to gain the benefits of a DSB, so far as I can tell, your idea appears to be both valid and supported by the experts. However I still think that it would be best served with an overal depth of just over 6 inches (plenum and sand included).
Now let me throw you a curve ball, so you can poke holes in my theory. For several years (4 now) as I stated previously, I've been running modified DSB in several small tanks at school. I followed the Jaubert method with three major differences. First, rather than a plenum, I laid a layer of cc covered with fiberglass mesh, my reasoning being that the water in the lowest level of the DSB becomes slightly acidic. A cc bed is poreous enough to allow standing water, and since the water is acidic, it should increase the breakdown of the cc, thereby adding calcium and other ions to the system, just as the break down of aragonite sand does. Thus in theory, I gain the benefit of the plenum, with the additional benefit of dissolving calcium to a usable form. Second, I've used only aragonite sand (although I do use a larger sand grain size for the 2nd layer) ~ recently tore down several of these systems to reset them (after four years running) and no concrete in evidence. Third, I don't add the second layer of fiberglass screen, with 4"+ of sand over the cc layer, no organism I've ever added (including a diamond watchmen goby) has ever burrowed deep enough to cause any issues. Now in four years, I've never had any issues or problems with hydrogen sulfide gas ~ perhaps because, as you stated, the presence of oxygen in the cc layer prevents the occurance of the gas. Give me your thoughts on this please Joe, thanks. BTW, sorry for the lengthyness of this post.

 

[florida joe]

Well first let me say that it looks like its “just you and me on this one pal” so with one and one half minds (your one and my ½) perhaps we can get soom good info out.
Lets start at the bottom of your system I believe you are saying in one of your tanks you put CC then screen then sand if so I think. CC not only being porous. Does not pack like sand and being at the bottom of your tank substraight you are not dealing with detritus build up to clog it? Any sand sifting species are keeping you sand bed aerated so you are getting circulation, and diffusion restricted yes but circulation nonetheless. I think your CC is acting as a modified plenum. Supporting the second stage of your filtration your aragonite sand.
With your modified CC plenum (if I may call it that) you are still getting diffusive flow from the body of water into the sand bed and into your CC or more specify the water around your CC there are no wholes in your system as far as I can see
LOL I just realized it seems as if I am justifying YOUR system.
When all is said and done I thing the ends just have to justify the means if it works for you, that’s all that matters.
Now let me throw you a curve. I may be going with refugium mineral mud to cultivate denitrifying algae (Cheato and caulerpa) thinking CC one-inch (your idea) screen and one inch ocean ( to speed up the seeding of my refug) sand and two inches of the mud. What do you think?
PS I do noth have that book but will google amazon right now thanks

 

[scopus tang]

Originally Posted by florida joe
http:///forum/post/2571258
Well first let me say that it looks like its “just you and me on this one pal” so with one and one half minds (your one and my ½) perhaps we can get soom good info out.
LOL, seems to me that your 1/2 brain is easily keeping up with my whole. Don't mind if others want to join they're welcome, it not, thats ok too.
Lets start at the bottom of your system I believe you are saying in one of your tanks you put CC then screen then sand if so I think. CC not only being porous. Does not pack like sand and being at the bottom of your tank substraight you are not dealing with detritus build up to clog it? Any sand sifting species are keeping you sand bed aerated so you are getting circulation, and diffusion restricted yes but circulation nonetheless. I think your CC is acting as a modified plenum. Supporting the second stage of your filtration your aragonite sand.
Correct, and I also believe that the cc is acting as a modified plenum.
With your modified CC plenum (if I may call it that) you are still getting diffusive flow from the body of water into the sand bed and into your CC or more specify the water around your CC there are no wholes in your system as far as I can see
Cool, I couldn't either, but it always helps to get a second opinion.
LOL I just realized it seems as if I am justifying YOUR system.
When all is said and done I thing the ends just have to justify the means if it works for you, that’s all that matters.
Chuckle! My intent was not to have you justify or adopt it, I really just wanted some feedback; if you thinks its a good idea and try it, great!
Now let me throw you a curve. I may be going with refugium mineral mud to cultivate denitrifying algae (Cheato and caulerpa) thinking CC one-inch (your idea) screen and one inch ocean (to speed up the seeding of my refug) sand and two inches of the mud. What do you think?
Well, first of all, I'm very jealous that you have access to ocean sand! Second, I think the refugium mud (at least what I have seen) is a very, very fine sand, which should pack even tighter preventing oxygen penetration. So my question here is, will you be introducing sand-sifting critters into this microsystem? If yes, then I see potential issues, as the sifting of the mud will allow oxygen to penetrate to the second layer. If not, then in theory it should work. My only suggest would be to increase the second layer (ocean sand) by 1/4 to 1/2". That gives you 4 1/4 to 4 1/2" on your DSB. I've found the mud to be an excellent substrate for growth, and since the grains are so fine, you may even have some anaeorobic bacteria working in the lower layers of it.
PS I do not have that book but will google amazon right now thanks
More than welcome, its an excellent resource for those who do not have the money or desire to have all the high tech. "toys" that are becoming so common in the hobby ~ great read for those who are young and just starting out and don't have a lot of money.

 

[florida joe]

Thinking of this since my refug is 36inches wide I may partition it off on center go with a mud based algae garden on one side and your idea of a deep sand and CC substraight on the other

 

[scopus tang]

Now that would be interesting, you could shut down flow through the refugium and test water from both chambers individually to get an idea of how each chamber is acting independently. Certainly think that you would be getting an ideal situation from the combination. Might have to consider that on the new system I'm designing to connect several of the DT tanks at school as an experiment. Very nice idea Joe

 

[florida joe]

Looking into your concern over the mud packing to tight and not allowing aeration with out some sifting species.
I may go with just Caulerpa and no Cheato. Caulerpa being a rooting species will root in the mud and thus help keep the mud from going anoxic since oxygen diffuses out of the rhizomes (have not used that word since college)during photosintises my good friend we may be on to somthing here

 

[scopus tang]

Originally Posted by florida joe
http:///forum/post/2571758
Looking into your concern over the mud packing to tight and not allowing aeration with out some sifting species.
Actually, I think the mud packing tight would be a good thing ~ assuming that oxygen is actually produced in the bottom level, rather than filtering down somehow. I think the thick mud layer actually would increase your chances of getting anaeorobic respiration going on the lowest layer of the mud and the midlevel of sand, which is what I believe you desire. I would suspect that introducing sand-sifting creatures may be detrimental. On the other hand, if the mud packs too tightly, then nothing will be able to transfer ~ too much, too little, or just right

hard to say. Can't find anything in written sources that says much about the mud.
I may go with just Caulerpa and no Cheato. Caulerpa being a rooting species will root in the mud and thus help keep the mud from going anoxic since oxygen diffuses out of the rhizomes (have not used that word since college)during photosintises my good friend we may be on to somthing here
Rooting algae seems logical to keep upper layer oxygenated and could on its own eliminate the need for aerating organisms. Sure you're aware of the issues with Caulerpa; would you try to maintain a 24 hour light cycle or harvest to prevent reproduction? I personally would go with the "grape" and stay away from the "fern" variety ~ of course with the grape you'll need filters between sump and fuge to prevent the influx of "grape" to the DT.
Haven't asked, how big of a DT and sump are you using with the fuge and how big is the fuge itself? How are you planning on plumbing the two (sump/fuge) together or is it a single unit?
Have to tell you, I'm enjoying myself here ~ like this type of discussion/problem-solving. Still waiting for someone else to drop the other shoe however.

 

[florida joe]

Well my friend lets talk about Mud. There is very little info to find regarding its use in a DT. I will be using it in my (now partitioned thanks to you) refuge. On this scaled down usage this is what I have learned so far.
Refugium substrate of mud cannot have strong water movement since the soft fine mud is easily suspended in the water column when disturbed. That is why I will only go with Caulerpa and not Cheato. I will however need a good turnover rate with out producing any current. I will try to accomplish this with a surface skimming effluent water delivery into my sump from the refug. The influent will be PVC pipe that I will drill numerous holes it to defuses the water so as to minimize velocity while retaining the same volume.
Oxygen depletion is a major concern in DT use of mud but I feel I will be fine with the refuge application my sump protein skimmer and egg crate cover should give me more then adequate gas exchange. I will also be illuminating the refug 24h so I will be getting constant photosensitize from my Caulerpa.
The mud side of my refug will ONLY contain mud. I can probably get by with a two-inch deep layer of mud but I will go with four to see if I can duplicate habitats for things that burrow deep in mud.
The Caulerpa will handle most of my nutrient export when I harvest it. Since they grow fast and I hope to harvest regularly. (And use the harvest as a fresh supply of food for my fish) One of my concerns however is the introduction of spoors into my DT. I will have to integrate a filter into my effluent before it dumps into my sump and hopefully not introduce the spores into the DT
I will try to go extensively with caulerpa taxifolia. I am leery of the grape verity because if it does get into my DT it can smoother my corals and is not easily removed.
As a side note caulerpa taxifolia the best choice for me has been discovered in a marina in south California and has caused legislation being passed regulating its import and sale. I am trying to find out if it only relates to that state as of now.
Now for the logistics
110 g reef tank
Wet dry bio ball and mechanical sump gravity feed by two internal overflow boxes
My refugium is 36 inches wide 18 inches high and 8 inches deep, which I believe, gives me just under 20 ½ gallons with out figuring in the displacement of water by the substrates
My pluming will be rater simple I will tie into the gravity feed for my sump. PVC into one bulkhead on the top of my refug. and dump water into my sump with a side bulk head at the other end I will valve both influent and effluent water to control flow.
I eagerly await your input on OUR project.
Joe
PS need info on lighting for the refug

 

[scopus tang]

Sorry I'm so slow getting back to you Joe.
Question on the refugium mud ~ are you using actual mud, or very fine sand? The reason I ask is because I'm currently using refugium "mud" in my sump/refugium. The "mud" I'm using is actually very very fine sand. In this sump/refugium combo (check out my thread https://forums.saltwaterfish.com/t/316767/yeah-upgraded-my-sump-refugium, I'm running a Quiet1one 4,000 High Head as my return pump, giving me just under 1000 gallons of flow through the sump/refugium. At that rate, once the mud was saturated, I've had zero issues with mud suspending into the water column. I believe that a direct flow onto the mud would indead cause issues, but with your PVC influent, if you direct the flow across the sump rather than down, I believe that you will have few issues.
I also believe that your gas exchange should be adequete, especially given that your caulerpa will also be producing oxygen as a result of photosynthesis. What type of burrowing organisms are you considering? I tried hermit crabs in my bog tank, but their constant burrowing created major issues with mud suspension in the water column.
So long as you maintain the 24hour lighting cycle and regular harvesting, I believe that your spore production will be limited, but I like you, still think some sort of filter will be required. The issue here will be find a filter that will prevent spores from crossing, and yet allow water to pass, and will not plug up too often on you. Perhaps the foam pond prefilters that slip onto the end of pipe?
caulerpa taxifolia, like the grape variety can also smoother corals, at least IME. However, so long as you maintain the precautions we've talked about, I believe you will be alright.
Originally Posted by florida joe http:///forum/post/2572205
As a side note caulerpa taxifolia the best choice for me has been discovered in a marina in south California and has caused legislation being passed regulating its import and sale. I am trying to find out if it only relates to that state as of now.
I believe that you are correct, the ban so far as I know applies only to California.
Originally Posted by florida joe http:///forum/post/2572205
Now for the logistics
110 g reef tank Wet dry bio ball and mechanical sump gravity feed by two internal overflow boxes
This will be a nice system; if memory serves, the footprint of the 110 is 6' long and 18" wide. I assume based on the internal overflows that the tank was drilled? I also assume that you are going to be running corals as well as fish. The 18" width will limit somewhat your options for aquascaping, but you'll be alright. Just out of curiosity, why the bioballs in addition to the refugium?
Will your effluent bulkhead sit lower than the influent bulkhead, so that you will have some additional gravitation force to feed back to the sump, or will you maintain them both as the same levels and simply rely on direct current?
Lights are something I really wished I knew more about. On my refugium, I'm running a small PC that uses two 10,000K lights, however my growth rate with chaeto hasn't been great. I know others who are running simple flourescent bulbs and getting much better growth rates. Given the depth of your fuge, based on what I know (which admittedly is not much), I would go with a regular flourescent light equiped with a bulb with the ideal light spectrum for plants.
Appreciate your including me as a partner in your project; I'm considering something similar for a system at school, although on a much smaller scale. My goal is to set up two DTs (a 30 long and a 20 high ~ or something similar) plumbed into a common sump also 20 gallons w/a seperate fuge (30 gallons) and a chiller; all on a single L shaped stand. My ultimate goal is to be able to keep corals w/ a few fish in the 30, and anemonies and corals in the 20 gallon. I'd like to be able to keep atlantic anemonies, zoas, and a few cold water fish species like black-cap basslets and purple firefish; so may plumb the chiller only into the 20 gallon DT. I won't be able to start building mine to mid June, so sounds like you may get started ahead of me.

 

[florida joe]

Thanks friend a by the way I do not know your first name. The mud is refugium mineral mud by CaribSea Inc. is very fine.
Sorry about the confusion my tank has been up and running for quite some time. Dimensions are 18X60x24high.
It hope to receive the refug tank this week I will post pics but he influent will come in form the top and the effluent fill discharge out the side three inches lower then the influent as per your suggestion I will elbow the influent so the water comes out parallel to the substrate.
My tank was set up seven years ago FO with CC and a wet dry sump that incorporated bioballs so they are grandfathered in LOL turned it into a reef about a year ago
Caulerpa is harder to get then I thought my LFS was not even selling any, he gave me a hand full of this that he uses in his refug he swears its caulerpa. Can you ID it I cant yet? It is in my QT iIwill try to stock pile what ever I get Also check out my thread in reef for the hitchhiker I got with it. (Any suggestions on keeping him)
For my lighting I am thinking of going with Zoo Med Flora Sun Fluorescent Bulbs don’t know what wattage just yet.

 

[notsonoob]

Just a side note.
I've been reading more and more that some advanced aquarist aren't using a sand bed in the fuge. Just have the algea on the glass bottom. Well, at least some...
I put sand in mine, as I figured that the bugs would like the sand too, but it has me scratching my head of the possibility. I see my cheato loaded with bugs when I first turn on the light, but they disappear as the light stays on.

 

[kelly]

Originally Posted by florida joe
http:///forum/post/2573983
Caulerpa is harder to get then I thought my LFS was not even selling any, he gave me a hand full of this that he uses in his refug he swears its caulerpa. Can you ID it I cant yet? It is in my QT iIwill try to stock pile what ever I get Also check out my thread in reef for the hitchhiker I got with it. (Any suggestions on keeping him)

Looks like Caulerpa prolifera, try searching on it in Google.

 

[florida joe]

Originally Posted by NOTSONOOB
http:///forum/post/2574045
Just a side note.
I've been reading more and more that some advanced aquarist aren't using a sand bed in the fuge. Just have the algea on the glass bottom. Well, at least some...
I put sand in mine, as I figured that the bugs would like the sand too, but it has me scratching my head of the possibility. I see my cheato loaded with bugs when I first turn on the light, but they disappear as the light stays on.
I in all likelihood will divide my refug into two sections one with a mud substrate over a plenum an the other sand over CC as per Scopus refug