I had the same problem a couple of months ago with a new piece of river driftwood. The stuff looks like a clear/whitish gel-probably fungus...I tried Pimafix first, with no luck. I then pulled the wood and soaked it outside in bleach water, in the sun, for a couple of days then soaked in rinse water for a week or so. The stuff came back soon after returning it to the tank. I added several dozen ghost shrimp, a CAE and two BNs. Somebody ate it. It disappeared and has not returned. I give credit to the shrimp. Good Luck.