[mulita]

That's a very nice idea! I bet if you can get it done your aquascape is going to look great!

If you are going to try coating with Polyurethane it may work, I would also suggest trying Polyacrilic as this is also water resistant (Mate, No gloss to try to keep natural look), however it would be a better idea try to find something similar close to a river as the wood really needs to be exposed to weather for long time, and even do it needs to be treated anyway as it will leach in some degree.

I have use dry wood collected in the desert with success. I treated it the same with a bleach/Water solution for several days (about two weeks or more) rinsing and bleaching again several times and finally long freshwater rinsing with dechlorinator. this method has also work for me with initially stinky pieces of wood (It takes longer but It worked for me in a piece that I really like so I made it work , I am really stubborn and have time [smilie=l

Whatever you do, try it separately in your tank, don't add fish or plants until you know for sure that the driftwood is not leaching, decomposing or altering in anyway your water chemistry.

 

[mulita]

How long it will take to leach out it certainly depend of the driftwood itself, you have to bleach treat them as much as needed until it stop leaching, changing the water speed up the process as ZerOzax said. Once tannins gives up, keep them in the solution for a couple days, rinse them, put them in water again and then leave it there for a week, do an ammonia test, if you got some reading, take the driftwood and smell it, if it stink it is the source of the ammonia, you may bleach treated again but chances are that this is not going to work, you may try it as it can give up an work.

As you said, this process is fun in all its phases and actually will make you proud once you finish up with a nice scape, and then you ending up adding a hobby to the hobby