unknown growth in the bottom of tank

[drpenquin]

recently ive been getting these hairy growths on the bottom of my tank. it never really grew until i added my driftwood and moss ball. any guesses what this is? doesnt look like algae to me

 

[FranciscoB]

It is not algal, but I believe probably fungal. I have seen that before in newish wood and it is harmless if removed relatively soon. I scrape it off and suck it during water changes. Generally it does not come back more than a couple of times until the wood 'ages'. It is probably harmless even if left in place, but it is not worth risking that it could colonized other places in the tank.