How can I do to get rid of it?
As unpleasing as the site of the white fuzzy film on the driftwood, it is harmless to the fish. Some fish, shrimps, and snails seem to have a liking to the fuzzy film and love munching on it. Before deciding what your course of action, my personal preference is always find a natural way to deal with any sort of outbreak or problem. In this case, since it’s a part of the decomposition cycle, I would just give it time for the fuzz to go away. The fuzzy film will disappear after a few days, or weeks.
-Fish such as otocinclus, bristlenose plecos (bnp), and snails will love to eat this film off for you; however, keep in mind that if you introduce snails into your tank….they may become pests to you in the future.
-taking the piece of wood out and scrubbing off the white fuzz when it looks too unpleasing to your sight
-treat the fuzz with one of Seachem Excel, metricide, bleach, hydrogen peroxide (I’m not too much of a fan for this method, but it’s worked for some people)