Exodon, you put a painted model in your tank? Don't most model paints still contain small amounts of lead? You put that in your tank?
And people use crazy glue? There's toxic stuff in that as well. Certainly perhaps if you used a very small amount, it might get diluted out by the volume of your tank. But if you've ever smelled the suff...that smell is what leeches into the water and can certainly do some damage.
Same with silicon, which is why it is usualy recommended to let it cure for at least a week, then to do a rinse first before you add the volume of water you will use with the fish.
Can't be over-cautious when it comes to your tank.
That's why in the matter of driftwood, I personally perfer to get my own rather than pay outragious prices for someone else to do for me what I can do myself. Fortunately I live near plenty of beaches, so I get my wood already de-barked, leeched, baked, and worn naturally into unusual shapes. The only thing I really do is soak it in water for a week (hot water poured over the wood changed daily) to simply get rid of salt build up.
If you live near forested areas, use dead dried wood, not fresh green sticks. Sap and tannis may cause your tank to become acidic, which will indeed kill your fish if not regularly flushed from the environment.
Be selective where you collect, pesticides are a concern, as well as exhaust fumes from traffic, industural discharge and waste, road-run off, and anything else humans can do to pollute the environment. If you wouldn't eat it, don't put it in your tank.
If anybody wants a really good read, might I recommend -From the Forest to the Sea: The Ecology of Wood in Streams, Rivers, Estuaries, and Oceans- by Chris Maser and James R. Sedell (St. Lucie Press 1994). One of the best books I have ever read myself, help with the research project I was doing on the effects of dams on the Susquahna River on drift-wood accumulation, and what effect the removal of said wood (usually hauled out and turned to firewood) might do to the ecology of our oceans.
~~Cole