I've never dealt with that one before..I will research it.
I have no salt in my pond now...so, that's not an issue. I salted in spring...but after a full season and many water changes, it's out now.
I read that article by REC. I'm really thinking it was just a low temperature..with seasonal fluctuations. Fall had been pretty warm..and it had gotten cold very suddenly. My pond is clean enough to eat off the bottom..and I cleaned out the filters before shutting down. I also did a 2ppm treatment of PP at 60deg. Things should be spotless!!! I have no trees over the pond..so leaves were minimal!!
Gotta just be the cold!!