I've been following this for quite a while, as I have a similar problem on a much smaller scale. Great post and info.

How about a timer based alcohol "injection" pump? Or maybe a condensate trap with a vertical riser (flat black aluminum would be best) that would extend above ground, drop temperature of compressed air and freeze out water, then heat up when the sun hits it and melt the ice back out. It would have to be somewhat large to catch enough water without plugging, and the base would need to be below the frost line to let the water out after it thaws. But it might drop the temp enough to keep the water from freezing out farther down the line.

Maybe one of the air compressor type condensate drains with a built in timer would work with less air loss / plugging potential.

Best of luck - we're still not frozen here yet, but we lost all of our fish in one pond last year. Keeping my fingers crossed.

They've gone to plaid.