Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
The softer, mushy parts will rot pretty fast in an aquarium.
Use a stiff brush (wire brush or very stiff plastic) and scrub off the soft areas. You may need to gouge them out with a knife. A little bit of this sort of stuff will not be a problem, but large areas can be.
Brush in the same direction as the grain of the wood. Wire brushing can damage the firm, good wood, making scars that may show even under water. If you brush with the grain of the wood, the brush may still scratch the part of the wood that you are keeping, but it will look natural, not like a scratch.