So I just gave Whiskey a 50% water change. While I was rooting around in his tank I happened to graze his driftwood. There's this stuff growing on it that feels and looks like wool and is dark brown/black. So what is it? It's only on the wood. The rest of the tank is clear of it. I took it out but I was curious. Here's a pic:
I really don't know. I'm thinking now it might be some kind of fungus. The water was really, really smelly. I did a 75% water change. Bleh! I'll do another change tomorrow. It smelled like something burning.
Driftwood sometimes will grow a fungus on it when first put in a tank, but this tends to looks more like snot then dark brown wool like. Could be something that is similar though. Is the piece newish or has it been in the tank awhile?
A dark brown algae looking substance is often a diatom bloom, but this typically would be growing all over your tank.
I have/had diatoms in all my tanks so I know it wasn't that. The driftwood is probably 7 months old. I have it in a 5 gallon planted hex. I took it out and scrubbed it of diatoms maybe 3 months ago with just hot water.
Look up-Green beard algae (GBA) (often seen on wood) and black beard algae (BBA) and see if they look anything like what you have, however, when I hear "smelly" the first thing I think of is bacteria or BGA- cyanobacteria-did it wipe away easy or does it seem to be stuck to the wood? It is hard to tell by the pic since you took it out of the water, but most likely an algae of some type and harmless on the most part.