To plenum or not to plenum...?

[Debbie G]

I am setting up a 175 gallon bowfront tank to eventually house a reef. I know that I would like jawfishes and that they need the substrate to be about six inches deep. (I'm not going to make it 6 inches deep in the whole tank, just a designated area). Will the sand/aragonite get stagnant or house toxic gases? Would installing a plenum eliminate that problem? Also, if I DO use a plenum, exactly how important is it to be sure that NO substrate gets under the plenum? Is it something to be neurotic about or no big deal if a little sand slips under? In case it makes a difference, I am planning on using a refugium in my sump. Has anyone had any experiences, good, bad, or indifferent on this subject? I'd so appreciate any input, as getting the plenum put together would be one of my first steps. Thanks!
Debbie G

 

[liquid]

Moved to the New Reefkeepers Forum

 

[hdtran]

If you look through the "Advanced Aquarist Online" archives, there's a very nice article about Jaubert plenums there.

I have one set up in my tank, based on the recommendation of my LFS, who has them set up in his 'show' tanks. He says that he's used it for 'years' with no problems.

You need not be paranoid about a little substrate falling into the plenum area. The plenum area is basically there to provide an area where water can convect freely. Dust or debris in the plenum area is not a big deal (but 1" of debris is...)

I personally would not do a partial plenum (plenum on, say, left half of tank, regular DSB on right half). From my reading, you want different size substrates for plenums (plena?), 1-2mm, as opposed to DSB (finer). Your jawfish will mix up all the substrates, so I would recommend that you choose one approach or the other, but not mixed.

On a final note, whether you are doing DSB or plenum, I would put in a layer of screen about 3" below the substrate level, to prevent the jawfish from digging all the way to the bottom. In either DSB or plenum, my understanding is that the theory says that deep layer needs to stay anoxic (not anaerobic, but anoxic). A jawfish (or other critters) digging all the way down would mix up the anoxic and 'oxic' zones. But here, I'm just regurgitating my reading.

I hope this was helpful.

Regards,

 

[hillbilly]

On a tank that size, if I wanted a plenum, I would put it in the fuge. From what I've read it only needs to be about half the sq. ft. of the tank. That way if you ever needed to remove it, you wouldn't need to tear down your tank. You would then be free to do with your tank bottom as you please without the plenum being in your way.

 

[Debbie G]

Thank you both. I'll let you know how it goes

 

[Anonymous]

Personally, I'd leave the plenum out if you are doing jawfish. It just seems like it adds an additional complication without any real benefit. The jawfish like bits of shell and rock mixed into the substrate also, as they can't tunnel well in straight sand.