Thanks for that additional point, esshup.

I have never observed a tannin fish kill or had a direct buddy that suffered one. However, there are Pond Boss "regulars" that say they have suffered a fish kill, and tannin fish kills are generally in the public literature.

I feel like we are missing some key element that is also part of the tannin fish kill mechanism. I just have no clue what constitutes the mystery factor!