Samartha,

> Another lady here had the same idea independently. Maybe there are
> some hidden sourdough genes which get turned on at times to cause
> this?

It's possible that some of the cross-pollination comes from
homebrewing, where it's very important to keep your wort at the right
temperature throughout fermentation. Too hot and there are off
flavors, too cold and the yeast don't attenuate the beer properly, or
stop working altogether. I got an aquarium heater for this reason, but
decided to build myself a fermentation box using a light bulb as a heat
source. Now I use the aquarium heater in a small bucket of water for
sourdough, just like you do, except without the pump. Works great.

BTW, great web site. Lots of good information, well presented.
Thanks,

Chris
--
Chris Swingley
University of Alaska Fairbanks