That’s a piece of wood that’s been in your tank awhile? Not something you just found in a stream? If the first you’ve got a lazy pleco. May want to get a bushy nose some SAE and a few ottos to eat all that algae up. Mine kept my wood free of that. Only thing is a little bba that may be on some. All that algae is harmless. If it’s bothering you yes pull the wood and scrub it off with a brush. 9 out of 10 times the pleco drops out as the wood leaves the water.