[GarterGuy]

I've used fir bark before, it's doesn't have as much of the caustic oils that say your cedar or such has, and it seems to be safe. Also I've found that it tends to get moldy when it gets wet. I had used it with a pink toe tarantula and it did fine and didn't have any bad affects from it, but I did find that the bark got moldy underneth the T's water dish.
Roy