WHAT THE HELL IS THIS STUFF?!!??!

If it just start to take place after almost year in the tank, and multiplying, I would not just leave them be. Take it and rinse, sun dry and rinse before adding back to tank.
Did you add any fish which produces heavy slime naturally or when irritated by extreme water condition such as Polypterus sp, eels, etc.

Maybe some fish spawned?
 
i had some very similiar stuff floating in my tank after rearranging it yesterday. I have no wood in there, just some amazon swords.
 
wow that slimy milky transparent mucous-like algae is annoying as hell. I just set up my planted tank a week ago with a large piece of driftwood that ended up getting covered with that stuff over night. I read about it in another forum and was heavily advised to take it out and either do one of the following: let it dry for 1 month, soak it in some sort of chemical bath for 2-4 weeks, or boil it for several hours. Since I was very impatient I opted out of all of those methods, took the driftwood back and got some malaysian wood instead.
 
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