Please help from someone who is sucessfully using Jaubert Pl

[mweber]

I converted my 180 to Jaubert about 1.5 months ago. About 3.5 weeks ago I turned off my skimmer per Galleon's recomendation. I have been sampling and testing my plenum conditions through a permanantly mounted 1/4" tube that is plugged most of the time. Originally I had same nitrate and oxy in tank and plenum. After a few weeks my oxy fell to 2ppm in the plenum, it is 7 above.

About 2 weeks after my oxy fell to 2, my nitrates slowly began to climb in the plenum. I now have 2ppm oxy and 17ppm nitrate in plenum and 7ppm oxy 8ppm nitrate in main tank.

Questions:

Doesn't this indicate that my plenum is not working?

Will it just take more time?

Do I need to limit convection through it with a deeper bed on top? Currently I have 2"CC with 2"oolitic on top. Actually my oolitic ranges from 6" deep to 1/2" deep as those darn fish won't leave it where I put it

Can you see critters running around in your plenum?

 

[Anonymous]

I have not set up a plenum, but I am going to when i set up my 100. The one thing you seem to be missing, (from my research only) is a sheet of screen between your plenum and your top sand bed. I think it is called a sand cozy?

It should go somewhere in the middle of your DSB so the sand sortin' critters will not disturb the bottom half of the sand bed.

Jsut my 2 cents.
B

 

[jmeader]

Crushed coral is a bit large for a plenum. The spaces between pieces allow oxygen to penetrate deeper. Crushed oyster shells would have packed more closely. Argonite of small particle size would have been even better. Bingo is right about keeping animals out of the lower region. I layed down about 3 inches of crushed oyster shells and covered that with fiberglass screen. Then added another 2 inches above it. You also need to be sure no light can get into the lower region. Do you have the bottom of the tank painted or taped over. Finally, Your system is still cycling. It will take 2 to 4 months for the plenum to fully kick in.

 

[Anonymous]

Mike, the problem is likely the sand bed depth inconsistancy. 2 inches of crushed coral with oolite on top does not make a good combination. Geo-Marine through and through is the best, as the plenum works ideally with sand sizes ~2 mil and above. Other than that, try to get the sand depth to stay consistent (to maintain the oxygen gradient), and give it some more time my friend.

 

[Anonymous]

Plenums seem complicated & too much of a hassle. (If I may be so bold

)

 

[ondria]

Newbie here... What is a plenum?

 

[smokinreefer]

reefkeeping seems complicated and a hassle compared to a siamese fighting fish in a bowl.

am i not right?

mweber,
what do you mean by 2"CC? people use the term CC somewhat loosely, what i want to know is particle size. is it like caribsea reaflor? or do you mean crushed coral literally, like the big a$$ed pieces commonly found in Afican cichlid tanks?

and how much oolitic sand are you using? when i had a plenum system, although much smaller than yours i used, crushed coral ~2mm in size. aragonite sand was not commonplace a few years back. anyhow oolitic may be a problem, fine particles tend to settle downwards, thus it will eventually fill up your plenum.

and from what i understand you do not want to have the plenum area/water exposed to light and to the main body of water in your system.

hope i can help you a little.

although my plenum system was only a 30 gallon tall tank, it was one of my best reefs.

oh sorry you did say how deep the sand was already.

well then, do you have some sort of mesh between the CC and the oolitic? to keep the oolitic from filling in the plenum.IMO your sandbed could be alittle deeper. How deep is your plenum( pvc and eggcrate i assume) construction?

i suggest adding a little more sand, maybe an inch. and you do need to find some way to keep the sand bed at a consistent height.

again, HTH just a little.

[ September 07, 2001: Message edited by: smokinreefer ]

 

[mweber]

I really appreciate your help.

My Plenum is about 1.5" deep supported by PVC and about 50 Blue bioballs spaced 3 or so inches apart. I have egg crate above it with screen on top of that. Next 2" of CC I would guess about BB size. Next 2 layers of screen. Next sugar size oolitic. I do have tape around the plenum to block light except a 2" wide peep hole for my curious eyes to see.

Have any of you tested plenum conditions or seen research on the nitrogen cycle with in a plenum?? Does it make sense that my nitrates would spike to above tank levels before beginning to come down?

What is the particle size of oolitic? Are you saying that my CC is too large and my oolitic is too small?

 

[Anonymous]

This may help.
Sand bed references.

I was doing a lot of research deciding wheter to go with a plenum or not.

I decided since I already built it for my 100 gal, I will use it when I ever get around to setting it up.

B

 

[jmeader]

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Originally posted by mweber:
<STRONG>
Does it make sense that my nitrates would spike to above tank levels before beginning to come down?

Are you saying that my CC is too large and my oolitic is too small?</STRONG><HR></BLOCKQUOTE>
In a word, yes. Before the plenum acts as a denitrator it acts as a sink. In other words the nitrates are drawn in before they are broken down. If your CC is bb size it is a little big but might still be workable. If your sand is sugar sized it might just fill the gaps somewhat. I doubt it would settle all the way down into the plenum unless the lower region gets stirred up by you or animals. So give it some more time and see what happens. It's the only way to learn, experimentation plus observation.

 

[smokinreefer]

yup, jmeader is right. nitrates will spike in the plenum before it can begin denitrification. cuz the anaerobic bacteria and what not need to increase in population according to amount of food(nitrate) for them to thrive. just part of the cycle. keep in mind, this spike should occur within the plenum and not in the bulk/tank water.

with 4" of sand atop your plenum i think it should be OK. but you want to keep it at a consistent 4" through out the sand bed. you do not want any low points, as it wont provide the anaerobic conditions.

it seems like your tank is doing fine, and that your just curious about the numbers your getting from tests. so just be patient and things should begin to balance out.

GL

 

[mweber]

Thanks for your encouragement guys. If I am successful, I will post the results in a month or so. If not I will ask for your advice. I got my tomato clown an anenome, and put the big black damsel in isolation sump so now noone is greatly messing up the floor.
I still would like input from someone who has actually watched the cycle in a plenum.

I also am curious if anyone who has a working plenum can peel the tape back and see shrimp and pods living in there.