In an undisturbed planted aquarium there
are some advantages to keeping nutrients
confined to the substrate and out of the
water column. Low levels of phosphate don't
encourage algae, for example, and low nitrate
levels work for the long-term benefit of
the fish. Chemotrophic nitrifying bacteria,
the ones in the bio-wheel and the gravel,
are competing with plants for available ammonia.
Though too much can be made of this competition,
once the nitrogen of ammonia has been converted
to nitrite, it is all but lost to plants.
Nitrate is an endproduct of bacterial activities,
and it ordinarily builds up in the aquarium.
Apparently plants don't begin to tap into
nitrate supplies until the local ammonia
supply has given out. Exporting nitrate accumulations
becomes the fishkeeper's responsibility,
one major motivation behind water changes.
But the "Jaubert" system that has
been adopted by reefkeepers can be adapted
to freshwater aquaria. If you aren't familiar
with the Jaubert plenum used by reefkeepers,
you should start by familiarizing yourself
with the way the system works in marine systems.
Run a www.google.com search "Jaubert+plenum." The Jaubert
system uses a "plenum," which you
probably already know is an undisturbed anoxic
zone isolated beneath gravel. There de-nitrifying
bacteria can metabolize nitrates, hopefully
rendering them back to gaseous nitrogen,
which remains dissolved in water and is eventually
outgassed into the atmosphere at the water
surface.
In the Jaubert system, it is not the empty
volume of anoxic water that counts after
all, for water supports few bacteria, compared
to the surfaces that contact it. In the "Jaubert"
plenum system, it is the adjacent gravel
surfaces that provide strata for the anaerobic
de-nitrifying bacteria involved.
Cercona makes rectangular slabs of the chemically
inert ceramic-glass-foam material it calls
"Cell-Pore." Cell-Pore has interconnected
pores of 50-400 microns. Because the material
is rigid, you aren't likely to inadvertently
disturb the anoxic water stabilized within
the pore system. Nor are sand-moving fish
able to destabilize the isolated anoxic plenum.
Cell-Pore is available in 1 inch thick 9"
by 9'"slabs ($24). This new material
was enthusiastically reviewed in F.A.M.A., February 1999. The manufacturer's website
has been moved to www.kentmarine.com (Cercona of America, 5911 Wolf Creek Pike,
Dayton OH 45426-2439, Tel: 1-800.453.2782
for orders)
Robert T. Ricketts has been experimenting
with Cercona's Cell-Pore, but his first reactions
were cool.
"I had a 75 gallon salt tank that I
converted to freshwater and it seemed like
a good time to try it. I think I set it up
over the holidays, so it has been set up
for about ten months. One thing I have noticed
is a big decrease in algae growth. It could
be other things of course; it's not a real
experiment with controls and variables. It
is food for thought, and it makes sense that
reducing the nitrates in the water would
reduce algae growth. There are no vascular
plants in the tank, so I don't know what
effect the Cell-Pore would have on them.
I suspect vascular plants get much of their
nutrients from the substrate if they are
rooted. My other freshwater plenums are done
with egg crate and foam sponge. I think I
would prefer the foam over the Cell-Pore,
except that the Cell-Pore should last a lot
longer."
