Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
That dirty hairy stuff does not look like diatoms, but it could be some form of algae or fungus with diatoms or other stuff stuck in it, or an algae that just looks brown. Diatoms are individual cells that grow stuck flat on surfaces. They do not have enough structure to grow into hairy things like that.
With no plants turn off the light.
If the room light is really bright the diatoms might grow, they seem to get by on less light than most other algae, but not zero light.
Diatoms need silica to form their bodies. If you can remove the diatoms then you are removing the silica, and eventually they will die out.
The white fungus-goo should be cleaned off occasionally. It is not really harming things, but it can get out of hand.
Is the substrate still cycling, still producing ammonia? Allow some ammonia to be present, it is helping you to grow nitrifying bacteria just like the fishless cycle.
I would remove the wood and scrub it clean, perhaps once a week or so.
Do not use anything to kill it, you may harm the growing beneficial bacteria.