At least it looked like a film...but when I looked closer it almost looked like fuzz, like mold. But it's clear-ish white.
Anyways, I just recently set up a 20 gallon and took a piece of driftwood from my pond outside.
I scrubbed it off really well, but I was afraid to bleach it because I didn't know if you should do that with wood because of how well it soaks up liquids and I was being impatient....but now I'm wondering if I should have because it has this weird stuff all over it.
I would put a picture here but they don't come out very well, you can't see what I'm talking about.
Does anyone know what this could be? And is it dangerous?
No it's not dangerous ...most wood of any desription will have a bacterial bloom as your tank is cycling....This is not harmfull, just unsightly..!!
You can either take the wood out if you can without wrecking the aqauscape and pour boiling water over it and scrub it again, or you can attempt to siphon off the white slime/ mould.
Once your tank is stable and has matured, any clean up crew be it shrimp or fish (oto's) will soon get it cleared if it reappears...