[AQman]

I am about to replace my old reef with a new tank and stand, the old setup is getting a little seedy. Anyways, I set the old tank up around 9 years ago and plan to do things a little differently. I'm not sure whether I sould use a plenum and whether or not I should put the thing in the display tank or the sump, or both.

The display tank will be 90-125g and the sump will be the old 55g.
What do you all think?

Stephen

[clown-t]

i have a plenum and wish i had the 5 in. of sand. my nitrates are 0 and have no complaints but wish i did the dsb instead.

[jw]

After researching various sites for setting up a plenum in the refugium I'm setting up, I decided not to do a plenum. What swayed me was a paper by Albert Thiel (www.athiel.com) titled "No Plenum". He had observed the nitrates increased in his test tank over a years time. Everything else I read indicated a DSB would work just as well without the potential for a problem. A plenum sounded like it was a lot more difficult to get it right, so I decided to reduce my risk and just do a DSB. I've had enough disasters on my own with out needing to create one.

[tlc]

i have never set up a plenum but maybe i will someday just for posterity. i have 3 tanks with dsb and could not be happier. just be careful what types of creatures you put in tank. some fish will destroy what you need as will some other little creatures.

[Toadally]

I had a tank a couple years back that had been set up with a plenum. It ran fine for almost 14 months, then it crashed.

The set up I have now is for the most part a Berlin system. I don't use a DSB - only live rock and just enough crushed coral to cover the glass.
I'll never use a plenum again. I believe that gases had built up under the sand bed and had started releasing into the tank.

[SPasse]

Hi All,

I would like to explore the plenum vs. DSB concept.

A deep fine sand bed is one of the most beneficial components to a reef aquarium that you can incorporate. It is the product of study of, and advocated by marine biologists like Rob Toonen and Dr. Ron, who actually understand marine sediment ecosystems.

In the early 1990’s, when Bob Gomens wrote his Natural Nitrate Reduction Method articles in Marine Fish Monthly, I set up my first Plenum System which was based on silica sand. With the exception of coil de-nitrate devices (which were very finicky devices to be sure) this was the first system that tested for nitrates at levels below the resolution of my LeMott test kit.

Of course, because the sand was silica based, it contributed nothing to the CA and alkalinity buffering of the system.

With regular CA and Alk. additions, this system worked rather well.

When the SeaScope article about a ”true” Jaubert Plenum was published I also set up a 90-gallon reef that used this approach. Again this system worked well.

At the time, the concept of a sand bed fauna community was not well understood, or at least I certainly don’t remember reading about it.

Sand, was viewed as something which “needed to be kept clean” using a combination of high order sand stirrers such as Gobies and manual intervention by the hobbyist. These systems were typically not “seeded” with micro fauna, and detrivore kits were not commercially available. Live sand was really only “live” in a bacterial sense, and perhaps did eventually contain some “life” that had “migrated” from the live rock.

The sand in a “by the book” Jaubert Plenum was 4” depth of a uniform particle size aragonite based sand, typically CaribSea “Seaflor Special Reef Grade” (~2.0mm)
At the time this particle size was advocated as being necessary for a plenum to function properly, because it would allow a “target” oxygen level of ~1ppm to exist in the plenum/gravel interface area to host the bacteria that converted nitrate into nitrogen gas.

Even if detrivore and fauna kits had been available, a 2mm sand particle size is not conducive to the fauna community that we are trying to create in a “truly live” sand bed.

One “variation” of the plenum theme that I have seen is to construct a plenum that uses fine sands, such as “Sugar Size olitic”.

Using this fine sand, as one would use for a DSB, causes me to question if these are really plenum systems at all. I.e. plenum theory always held that the “magic” oxygen number for the plenum area was supposed to be ~1ppm, and a plenum constructed of 4” of “Sugar Size oolitic” would cause the oxygen level in the plenum area to be very much lower than that. So maybe the plenum in this scenario accomplishes nothing?

Finally, although this certainly does not happen to everyone, I have seen older plenum systems where (for whatever reason) the water in the plenum area which is very high in nitrates, suddenly migrate into the main water column. The resulting overall nitrate spike caused a vicious “hair algae outbreak”, and I find DSB’s actually easier to set up than plenums.

Regards,

Scott