Re: [APD] Re: Substrate Heating

["S. Hieber" <shieber at yahoo_com>]

Bill isn't a champion of substrate heating coils as far as
I know and I'm not trying to pick on him. But I am going to
jump on these notions from Dupla and Dennerle that 
beneficial convention currents come from substrate heating
coils. 

I don't think anyone has actually demostrated that
substrate heating coils cause significant convection
currents in aquariua substrate. If I recall correctly, a
couple of folks have measured slight tempreature diffs very
near and inbetween high wattage coils. If there is current,
it could be the same water going back and forth without
mixing in the water column -- who knows? And if there are
currents, it woud seem they are not strong enough to make a
diff in plant growth -- that they don't move anything in
and out of the substrate any more than plant roots
themselves. And if there are significant currents it could
be as some have suggested, only if the coils cycle
frequently and do not run constantly. 

In fact of the two major proponents of coils, the Dennerle
theory of benefit seems at odds with the Dupla theory. ONe
says they should be relatvively low wattage to work; the
other says they need to be relatively high wattage to work.
I suggest they can't both be right but they could both be
wrong.

Scott H.


--- Bill Wichers <billw at waveform_net> wrote:

> ... For example, the water around the
> heating wire will 
> move up and cooler water will replace the heated water as
> it moves, and 
> this happens as a continuous process. If you evenly heat
> the entire 
> substrate, the water won't move since there won't be any
> localized areas of 
> hot/cold.
> 
> Even if you use sand, the area around the wire will still
> be slightly 
> warmer than the rest of the sand bed and you will have
> convection currents 
> -- at least until you raise the entire sand bed to the
> warmer temperature 
> which is a condition you normally try to avoid with
> heating cables.


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