One possible grow medium that might be considered somewhat comparable to Hydroton (expanded clay pebbles imported into the USA from Germany) is Buildex, an expanded shale product produced at a quarry located between St. Joseph, Mo. and Kansas City, which is only about 150 miles south of my location near Omaha, Ne.  The company sent me a 10 pound sample of the material to test. Today, after several weeks of letting a handful of the material sit in pH neutral snow melt (see attached photos), I…