This white fuzz appears on only certain pieces. From my understanding there is no know reason for it. I sell tons of wood to lfs among other things. for wood i sell Malaysian, Mopani, and unknown roots on slate. I've never had this issue with the malaysian or mopani but the roots are like a 1/200 return rate with reasoning white fuzz. I've only ever heard one store say that the fish in that particular aquarium died off. I've never known the fuzz to ever subside.