Have you used any tar inside of it? Tar will produce a soapy
looking sudsy type that comes to the surface of the water
after a period of time. I imagine that other substances can
cause the same. Stones tend to be porous, so if you've
washed a stoney area with detergent, that could be the
cause. Maybe the stones around the pond contain some
kind of what not. When you said soapy, I was thinking
sudsy, but perhaps you should get the pH of the water
and see if it's an alkaline based thing ?

Just throwing ideas up.

http://www.btinternet.com/~herbie/pond.htm

--
Jim Carlock
http://www.911forthetruth.com/
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