i searched this for hours a few days ago. it's a fungus that eat dead wood once it enters water. if it annoys you, scrub it off, either way, eventually it will run out of nutrients and die off.
edit: nvm i looked closer at the pic, and it is staghorn hahaha
Last edited by Finnish_AE92_Racer; 12-04-2014 at 08:14 PM.
Reason: incorrect info