I'm still confused by what 71 tanner has said in various posts - in one he clearly says he has had a nitrate problem for quite some time, and that the nitrate in this tank regularly tests out at between 60 and 80 ppm. But in response to Pat's recent question above, he says his water test for nitrates was zero - this is completely contradictory - do you have 2 sources of water, 71tanner ?
As for the wood, it occurred to me there could have been the possibility that the particular piece that 71 T bought from that 'pet store' had previously been used in a display cage (say, a tank) for housing another animal, such as a reptile (and therefore exposed to toxic contamination seeping into the wood from urine or feces - whatever- and then, upon sale of that animal, perhaps that particular piece of wood was accidentally placed back into the store's box containing other aquarium driftwood for sale, and that's the piece that 71 T actually bought ? This may seem farfetched, but these kinds of things do happen on occasion.
This wood was soon taken out of the tank, but the damage had already been done if this was the case.
Just a thought as to this possibility.