Re:Yet another plant tank design

>I have had the idea of
>placing eggcrate or something similar in the bottom of the tank and placing
>a couple of the 7.5w heaters under it (not resting on the glass). I have
>thought this would possibly work better than a UGH not to emntion the fact
>it would eliminate the unsitely lift tubes.
>My thought was that by heating the water under the substrate it would rise
>through the substrate drawing cooler water down into the lower water
>chamber. In theory it should work much like heating cables.
>Does anyone have any comments about this concept, good or bad and has anyone
>tried it yet?

I think this should work.  However, don't expect even flows, and do expect some 
of the convection to be completely contained within your plenum.  Also, make 
sure to provide a way to remove the heaters in case they fail.  I've read 
reccommendations to replace heaters every year or two to prevent the 
thermostats from sticking.  If you intend to follow this regimen, you will 
definitely want some method of access to the plenum.  Alternately, using low 
wattage heaters like you plan, you could add a separate temperature controller 
to control the power fed to the heaters.  This would alleviate the potential 
sticky thermostat problem.  Or maybe 7.5w heaters don't have thermostats 
anyways.   :-) 

David W. Webb
Enterprise Computing Provisioning
Texas Instruments Inc. Dallas, TX USA
(214) 575-3443 (voice)  MSGID:       DAWB
(214) 575-4853 (fax)    Internet:    dwebb at ti_com
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