Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Ditto the above.
I am not sure if it is feeding on dust that has accumulated on the wood, or on the few dead wood cells that are soft enough for the fungus to get into, but whatever they are feeding on it does not seem to harm the tank.
I simply remove it if it gets too massive, without being fanatical about it. It will come back while the tank is cycling, but many aquatic creatures will eat it, especially Loricariads.