I think you are concerned about something that isn't really an issue.
In a reef tanks with a lot of powerheads, lights, pumps & flow, the
bottom of
the DSB couldn't be much of a different temp at all. I would imagine.
shrugs shoulders

Pszemol wrote:

"RicSeyler" wrote in message
.. .

But you DO want that oxygen-free area at the bottom of the DSB.


I have done some more reading about freshwater heating cables
and now I know what you were talking about: freshwater folks want
to encourage convection water currents using heaters. Warmer
water circulates to the upper layers of the substrate inviting colder
water to the bottom layers... This way they avoid oxygen-free areas.

Thanks for mentioning this, Ric! Now I need to do more thinking ;-)


--
Ric Seyler
Online Racing: RicSeyler
GPL Handicap 6.35

http://www.pcola.gulf.net/~ricseyler
remove –SPAM- from email address
--------------------------------------
"Homer no function beer well without."
- H.J. Simpson