Ted,

Okay - thanks! I spoke to the Gentlemen with Beckermill and sent him information on my pond. Of course he says his is the best like they all do. I guess his is a single diaphragm but can pump as much or more than the superior brand double diaphragm. FYI for those interested, the Superior brand and the Koenders brand are owned by the same group. They compete against each other but are very similar I have been told.

Here are the three websites for anyone interested:
http://www.koenderswindmills.com/
http://www.truewest.ca/wind/Beckermills.htm
http://www.superiorwindmill.com/aeration_systems.html

Anyone have any experience with Superior or Becker Mills? They all sound like they are well made but don't want to make a decision only on price.