If there is white slime on the wood, yes it is completely normal. I'm not 100% sure what it is but it happens with almost all new wood that was not pre-soaked. It's not strictly mould as mould cannot survive underwater. It will pass. Shrimp and snails both like to eat it, in the meantime.
If you can, get some shrimp and/or snails. I know first hand how horrible it can be, and @Tim Harrison will tell you too. But it WILL pass, time frame varies so we can’t really say when. DONT scrub it, siphon only.