On Fri, 4 Jan 2008 11:13:58 CST, Hal wrote:

Thanks! I've never considered freezing over a serious problem here.
I did drill a couple holes to see how thick the ice is, and dropped
the water level enough to pull the water away from the hole near the
center where the air bubble formed first. Mostly in fun, because the
10 day weather forecast shows lows above freezing and highs reaching
the 70's after Saturday. (It is about one inch thick.) Surprised me.
It seems the hot tub being elevated above ground by a skirt is quite
different from the other pond with so much ground contact. It has
been fun playing with the ice.

This is what can happen in a stock tank w/bubbler:
http://users.owt.com/jjspond/koipond/photos/set1/22.jpg

Ice freezes on top and around the sides, then the air going into tank lifts
the whole shebang. Including plant baskets. This actually lifted two more
inches before the air escaped. The amazing thing was, to my knowledge, all
the little fantails I had in this tank survived! ~ jan
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Zone 7a, SE Washington State
Ponds: www.jjspond.us