Sorry, Cap. Yes, 2 ppm meaning dissolved oxygen (D) for short. When I read your background info, I just thought that I would mention that yellow perch are more tolerant of low dissolved oxygen over the winter than most other pond fish. If anything survived, it sure could be the perch.

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From Bob Lusk: Dr. Dave Willis passed away January 13, 2014. He continues to be a key part of our Pond Boss family...and always will be.