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[APD] Re: Substrate Heating

Wouldnt say a heating pad, or terrarium heating pad
affixed on the outside of the glass do the exact same
thing as a substrate heating coil? or is there a
significance to it's being directly in the substrate? it
seems to me little would be different in this scenario
excpt maybe the amount of heat needed, maybe not even
that? isnt the amount of heat needed to create the
convection currents relatively low? and i do use sand
which i believe distributes heat evenly and easily?
so many ?'s in my posts hehe

If you distribute the heat evenly then you won't get convection currents. Convection currents only occur when an area of higher heat can move against an area of lower heat. 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.

You need very little thermal gradient to allow for convection currents, but there needs to be a *gradient*, which requires localized heating such as what you get around a wire. If you're just looking to heat your tank evenly, a regular submersible heater will be a lot easier and work just as well. If you want convection currents in the gravel use a heating coil. IMHO, heating pads underneath the tank aren't worth the effort.


***************************** Waveform Technology UNIX Systems Administrator

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