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Re: Aquatic Plants Digest V4 #572

 Subject: Re: CO2 regulators & heating cables
> On Wed, 27 Sep 2000, Shawn Prescott wrote:
>> The purpose of a cable heater is to bring constantly , new water full of the
>> needful nutrients to the roots of the plants, therefore if one uses it with
>> a thermostat, so that it can be in the "off" position about half the time,
>> then no new nourishment is obtained during this time.
> I seem to recall that it was George Booth who originated the idea that
> heating cables would set up currents in the substrate and thus transport
> nutrients from the water column to the roots.
> I also recall George saying that he doesn't have empirical data to support
> that theory.  Shawn, have you completed experiments to prove this happens
> in a typical tank setup?  If so I'm interested in learning about the
> turnover rates you measured and the methods you used to measure them.
> Roger Miller

I spoke with Claus of Tropica about this for some time. The amount of
turnover was actually quite high, perhaps too high for better root growth
using cables. They did one exhaustive tank experiment on this and found a
very low rate of turnover for an optimum flow. This would concur with many
healthy tanks without cables. Folks with cables tend to be a well financed
lot who can afford good lights/CO2 etc and have given over to all that would
make a nice planted tank a reality.

 I came at this from a very high flow(RFUG's) perspective and why etc this
worked well also.
Data on this is very difficult to gather and would be very labor intensive.
Observational rather than hard data is likely the way to judge this for most
of us.  
I would like to do some studies on this someday though. Namely the fauna
involved and the flow of nutrients.
Tom Barr