Dave, I wonder if something else good of been at play, Pallets,Xmas trees, floating cedar, oaks maples have always been standard structure additions in northen ponds.Many docks installed with treated CCA lumber. No problems that I am aware of.Sorry to hear you had the problem, I would of had our health dept test the water to see what exactly in the tannin caused the problem as would seem that some of the residue would of still been in the pond soil to resuspend when refilled, perhaps not enough. Please pass along if you hear of this happening to anyone again and what the particulars were as hate to lose another pond. Ted
