I'm new to this very useful group, and thought I'd add some of my experience with an aerating windmill.
My 20' Koender windmill has been up through its first winter now and I'm very happy with how the aeration has eliminated the sulphrous smell for our heated horse water trough. Although on some very cold still nights (below -25C) ice formed over the hole, most of the winter had a 6-8ft opening -- even though ice on other parts of the pond was 8-12" thick.
The aerator is ~8' below the surface, and I opted for a double rubber diaphragm unit that makes significant turbulence even in low wind.
Anchoring tip: around here, pouring concrete posts is about the only way to ensure that frost won't cause the base to tilt. However, I was challenged about how to set the posts accurately enough to clamp the base to them later. My solution was to construct the lower frame first (just the first 4' section), so I could position it on blocks with the anchor posts clamped in place but dangling into the sonotubes. When I poured the concrete, it hardened around the posts, and I could loosen the clamps to build the rest of the tower.
My nephew and I built the tower and blade assemblies in a barn (where it was cool!), then carried each out to the site. Each is just manageable for two people to carry, but wear gloves and watch the edges!
Since I knew the anchors would fit exactly, we blocked two feet and raised the tower so the end was ~8' off the ground supported on some wooden posts. The two of us were then able to slide the blade assembly into place using the tractor bucket as a platform. Raising the windmill was easier than I expected: we just kept adding longer posts to lift it a bit at a time until it got to a tipping point. A rope tied to the top helped me take some of the weight as my nephew guided the 3rd foot into place.
Unfortunately we were too busy to take pictures of the process but here's what it looked like last fall and in early March.
End of September 2005. I took the picture from the roof of our nearby horse barn. The inlet for irrigation and horse water is ~5' out from the diagonal logs, and about 6' below the surface.
March 5, 2006. The aerator keeps the ice away except on the very coldest days, but even then it only takes a day or so to open up again.
As you can see, the pond is fairly small: we had it dug out 8 years ago from a marshy area. It has a constant flow from nearby springs, and has seemed quite healthy. However, vegetation decaying at the bottom had been making the water smell bad during the winter, and algae bloom in the spring was a concern. There are plenty of small fish in the pond -- although otters come by for a cleanout whenever they get to 5-6"!
There may be better windmills out there wickedinhere, but I hope you'll be as happy with yours as we are!
