On the subject of driftwood, are there certain species that need to be avoided? I have heard that you should only use hardwood species, but I don't know if there is any truth to that. Conifers are a lot more resinous to begin with, but I wonder how much is left after the wood has soaked for years.
The reason I'm asking is because I am thinking about adding some wood to my tank. The flood control reservoirs around here are full of Douglas Fir stumps (with some nice roots attached) that have been underwater for forty to fifty years. The reservoirs are drawn down right now, so there is tons (literally) of white-bleached driftwood for the taking. There may be some hardwood stumps, but it can be hard to tell once all the bark is gone.