I have mopani wood in my tanks, One piece of it grew a strange whiteish spider web type mold (?)... Like a wolf spider would build his little web cave, but flat across areas of the wood. none of my other pieces had this same stuff. (most was like greyish hairy mold stuff, which I guess is ok, because it finally went away for me.)
In that tank I had little white bugs hatch. They attacked the plants I had in that tank too.
Just wanted to share that experience so you can watch for the thick webs. I would say if you see flat spider web things appearing on your wood take it out and rinse it off, but again it could have been coincidence. The white bugs might not have come from the web things, they may have just liked eating them or something. I had to take that tank down and completely redo it to get rid of the bugs.