White Fungus?

[hq25]

I have had my tank for 18 months now and recently i have had a growth of what looks like cotton wool growing on one piece of drift wood i have in my tank. i have taken it out and cleaned it and also have done a water change but after about a week it has grown back, i have other pieces of wood in the tank but it is only growing on this one piece. is there anyone that can help. many thanks

 

[WILDER]

Soak it in a fungus med, then rinse well, let dry out for aday before you add it back to the tank,.