good day to all....I think that this is a moss...not sure...it's this safe in my tank???
ammonia0, nitrite 0, nitrate 20

i760.photobucket.com/albums/xx243/cvl1919/SDC10543.jpg
i760.photobucket.com/albums/xx243/cvl1919/SDC10546.jpg

what type of wood do you have there? Is it anywhere else or just on the wood?

It could be one of several things looks like a fungus or something...for now I would remove the wood and give it a cleaning with a scrubber and a tank water rinse. I would also increase the frequency and amount of water changes for the time being.

You could also try to cook the wood. It sounds a bit wierd, but some fungus or/and bacteria can't stand the heat of cooking.

looks like some kind of algae or fungus. Take the wood out and scrub it real good with hot water. If it looks better place it back in. Keep an eye on the regrowth. I may be a problem of the type of wood your using.

Looks like some sort of algae, possibly hair algae which is a bugger to get rid of. I would scrub it off and remove it