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Plenums and filtration

>Scott asked:
>"On filtration:    Has anyone thought on the feasibility of a jaubert type
>natural nitrate reduction for the planted aquarium?"

Tom Wood wrote:

>I have a 60 gallon with a Jaubert style plenum in the bottom of the tank.  I
>put it there to take the place of the undergravel heaters, the idea being
>that I would get a higher rate of water flow through the substrate.  I'm in
>Texas where it's hot so that any heating devices are rarely on.  The plenum
>works only too well at nitrate reduction, I have to add relatively large
>doses of KNO3 to maintain nitrate in the 5-10 ppm range.  Whether it helps
>substrate circulation (or even if THAT is a good thing) is still debatable.
>The substrate is 4" of 2-3 mm silica gravel supplemented with topsoil high
>in clay content over a 1" plenum.  I use PMDD and Jobe's sticks under the
>heavy root feeders.  In retrospect, I wish I'd put some laterite or
>vermiculite in the plenum itself so that any roots that make it into that
>zone could take advantage of the CEC sites in an anaerobic environment.

Of course there are also lots of us who run planted tanks without plenums
or substrate heating who have to regularly dose our tanks with KNO3 to keep
nitrate levels measurable.  So I'm not convinced that it's the plenum that
is doing the job.  If your plants are growing well, they don't need any help.