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Re: Jaubert system
On Tue, 2 Mar 1999, Scott Matkosky wrote:
> Hi all, this is my first correspondence, I'm currently a student at St.
> Lawrence University in northern NY. On filtration: Has anyone thought
> on the feasability of a jaubert type natural nitrate reduction for the
> planted aquarium?
I have several tanks setup with an unused UGF plate under the substrate -
essentially a jaubert plenum. I've never seen behavior in these tanks
that I attribute to the plenum.
Some years ago I looked into using the jaubert system in freshwater tanks.
That involved mostly running through some fairly detailed mass-transport
considerations and talking with reef keepers who experimented with the
method quite a bit. I couldn't get the straightforward mass transport
problem to work out in a way that made it look like the system should work
and the most experienced reef keepers I could find told me the system
worked because of the nutrient cycling in the live sand, not necessarily
because of the plenum. Made sense to me.
If you can maintain a live substrate then I don't know of any reason why
it shouldn't work in a freshwater tank. But in a planted tank you've got
a couple problems.
1) The plants tend to aerate the substrate. In a coarse-grained
substrate with little organic detritus conditions may never become anoxic.
In a mixed grained substrate or a substrate with moderate amounts of
labile organic material, you may find local zones with nitrate-reducing
conditions and that is probably the ideal case for denitrification in a
planted tank. If you step over the line and your substrate is fine
grained and/or contains a large amount of labile organic material then the
oxidized zone around the plant roots may be small and big parts of the
substrate can become anoxic. I speculate that under those conditions the
redox potential in some zones will drop right past denitrification and
into sulfate reduction. Bad news.
2) In many planted tanks the plants use all of the available nitrogen and
plant growth may be nitrogen limited. Any additional competition for
nitrogen promoted by a functioning jaubert system would be detrimental to
the plants. Also, without nitrate in the system to buffer the redox
potential, I speculate that anoxic zones in the substrate may drop from
aerated conditions directly to sulfate reducing conditions. Do not pass
Go. Do not collect $200.
3) I don't know of many freshwater tank keepers that intentionally
maintain a "live" substrate supporting a population of nemotodes, small
annelids, flatworms or so on. In fact that could be quite difficult to do
because of the high predatory loads maintained in many tanks and the low
labile organic content of the substrate. Many of us do keep populations
of burrowing trumpet snails and those seem to fill a big niche in the
substrate "ecosystem", but I don't know if they are enough to promote the
substrate nutrient cycling that my reef-keeper acquaintances thought was
important.
Roger Miller