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[APD] Under Gravel Heating



To all,  mostly George Booth who's site I was just reading (thanks for such a great site):

I was interested in the effects of under gravel heating, specifically cables.  Personally, I have an established (read: it's got 'stuff' in it<g>, by no means a great planted tank, yet ;-) 90g aga and was wondering how I could incorporate under-gravel heating.  I have a nice substrate of laterite and 2-3mm gravel.  My plants seem to have great root systems after they've had time to establish themselves, but I was also reading the effects, or lack of effects, of laterite without additional heating.  This brought me to wonder how I could add heating to my gravel, without disturbing the tank too much.  Initially, I thought it can't be done, but anything with time and patience can be done.  And then I thought, why do I have to put coils under the gravel?  I don't recall ever seeing it mentioned, but it always seems people lean toward coils under the gravel!  This to me seems possibly dangerous, and difficult for maintenance.  My thought was to put an under-tank heating 'pad' somehow...

A heating pad, under the tank, first wouldn't be putting anything electrical in the tank.  Second, removing or maintaining such a device would be rather simple, like an external canister, because it's physically outside the tank.  Third, a heating pad won't shift like coils possibly can.  Fourth, the surface covered by the pad would be essentially heated very evenly!

The downsides I thought of to this were that the pads are also exposed to air, an undo amount of energy would actually go to heating the cabinet itself.  I don't see much of a problem there, possibly insulating the underside, exposed part of the pad would lessen these effects.  But also, the temperature differential from the underside of the glass to the top side.  I've seen on more then one occasion, glass practically exploding from heat differentials.  In this case, I wouldn't think there's enough differential to actually cause the glass to shatter, and on the flip side, under-gravel coils would offer much the same conditions, only from the other side.

Thus, I leave the list with this question:

Is it feasible to add under-gravel heat by adding a heating pad to the underside of the tank glass?

-Dave
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