Sealing wood / Waterfall Question

[rollei]

I collected some drift wood from my local lake. Is it necessary to seal the wood before adding to the background / Viv?

One of the pieces of wood looks like a natural stream; I plan to make a waterfall with it:

(My arm really isn't that fat, the camera is playing tricks. I'm actually really skinny)
I'm afraid this will rot. I had the idea of putting silicone and rocks to prevent this. Input anyone?

[Julio]

it is not nescesary to seal it, i woudl however sterilize it by cooking in the overn for a few minutes.