Sometimes patches of whitish fuzzy Saprolegnia appear on bogwood that's recently been placed in the aquarium. Though wood in oxygenated water at neutral pH values is almost always decaying, however slowly that may be happening, you don't want to encourage visible patches of fungus. Resist any temptation to attack the fungus by adding something toxic to the water. Don't haul out the wood and boil it in saltwater either. Be patient. As the aquarium matures, fungus on wood won't normally trouble you; in fact, bacteria are much more prominent than fungi as bio-degraders in submerged environments. Stronger light will encourage a thin coating of sessile algae, which soon brings the protists that feed on algae and on the fungal spores; the algae and bacterial polysaccharides form the basis of an increasingly balanced biofilm that will appeal to grazers like Epalzeorhyncos siamensis or Otocinclus and other Lory catfish. And the result of their grazing is that, though the spores are everywhere in water, patches of fungal hyphae don't get a chance to develop. Tannins in the water reduce the bacterial and fungal load too, so it's possible that peat filtration would have some slight positive effect in controlling fungus.
But if fungus is bothering you in a new tank or on a fresh piece of sunken wood and you want to help the bacteria and biofilm crowd it out, try this. Grip a small toothbrush against a siphon tube and hold the bristles over the end opening with your thumb. You'll find with a little practice that you can gently brush off the patch of fungus while you simultaneously siphon the loosened bits away. Be selective. Don't disturb adjacent areas, where a bacterial film is establishing itself and crowding out fungal spores.
