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Re: Dupla Cables

George Booth wrote:

> I presented my HYPOTHESIS that heating cables produced
> convention currents which caused nutrient laden water to be pulled
> into the substrate where the nutrients were attracted to the negatively
> charged binding sites provided by laterite. Thus stabilized, the
> nutrients were available to plant roots for adsorption. This system
> is also HYPOTHESIZED to maintain a sufficiently (not overly) fertile
> substrate by constantly replacing the nutrients adsorbed by the plants,
> thus avoiding long-lasting and well documented problems caused by
> starting with an overly and usually poorly controlled "fertile" substrate.

Recently I received some Dennerle which make the "Boden-Fluter" heating
system (not available in US) available in various wattages (100 watt is
recommended for 300-1000L tanks).

What I found interesting is their reasoning, some of it also consistant with
1) By warming the substrate, increased matabolic rates of micro-organisms
    within the substrate encourage anaerobic condition through their
    (increased) consumption of oxygen
2)  In their overall substrate strategy (rich 'mineral' bottom later
followed by
    gravel), the heating coils are supposed to move the nutrients from the
    lower layer to the gravel. The theory is that this mimics tropical
    where the lower depth soils are richer in humus and the nutrients in the
    humus are delivered to the upper soil layers by gentle water movement.
    Thus the cable mechanism is to support convection based nutrient
    mixing between the different layers of their substrate.

I don't see any mention in their literature about what type of temperature
they are attemptng to produce.

Christopher Coleman
christopher.coleman at worldnet_att.net