i recently bought a 2 foot piece of mopani bogwood for my piranha tank. i then soaked it to get rid of the tannins for about 2 weeks. my problem came when i put the wood in my tank. after a few days weird white fur started growing in random places???? i then took it out again and scrubbed it with a nail brush... only to find it didnt make a difference once i returned it to the tank... grrr!!! any suggestions?