Terry and others:
I read about this problem awhile back but I don't remember where (maybe the old board before it got hacked?). Pretty much everything Dave is saying is accurate. The main problem is putting in too much green wood at one time for the amount of water you have. Any green wood can cause this problem and there were even warnings about putting in too many christmas trees in one year. Dry wood should be OK because as the trees dry the tanins evaporate along with the water, alcohol and other liquids in the wood. I also remember it mentioning the testing that Dave is talking about as the only way to know if the wood is dry enough that you don't have to worry about it. If the water doesn't discolor noticably you should be fine - you shouldn't have to worry about actually putting some fish in the sample, just watch the color. If you aren't sure, get some pH strips and test the pH in the water sample and check that against the pH your local experts say you should have. If I remember right, the tanins throw the pH way off so you should be able to have a more scientific reassurance if you want to go that way.
This also applies to adding wood later on. I have been putting in some christmas trees each winter, but I try to limit it to about 10 or less average sized trees per acre per year. You might get away with more, but as Dave has testified, I wouldn't push it - it's basically irreversible if the water turns tanic. I've also pulled lots of old dry wood into the shallows in the summers and I don't worry much about that since it has always been really really dry wood.
Hope this helps.
