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Re: undergravel/undergravel heating drawbacks

Cavan wrote:

> Roger Miller wrote:  "UGF also limit your choice of
> substrate materials and your ability to use substrate
> fertilizers and amendments."
> This was what I meant when I gave the example of the
> jobes spikes.  I'm guessing now that any water
> movement through the gravel my substrate heating would
> be to slow to cause this same problem.  Is this
> correct?

*If* the cables cause circulation then it's possible.  I'm not entirely
convince that they do cause convective circulation, but then I don't
think that they have to cause circulation to be useful.

For every drop of water that circulates into the substrate there's
another one that circulates out.  The circulation rate is low
(presumably, anyway -- I don't know that anyone has ever measured it) so
you wouldn't expect a big effect.  However, if you put a source of
readily soluble nutrients (Jobes spikes, Planttabs etc., etc.) into a
zone where the water is moving up then most of those soluble nutrients
might be flushed - slowly - upward into the water column.

There are probably some substrate materials that you wouldn't want to
use with cables.  I think (and correct me if I'm wrong) the Dupla method
calls for a gravel+laterite substrate.  Anything close to
gravel+laterite would probably work reasonably well, but a clay soil for
instance might be a bad choice of substrate materials to use with

[Please note.  I don't use heating cables and never have.  I accept on
the testimony of those that do use them that heating cables are a Good