its a weed. i wont hurt anything but it may cover something that you want to grow. and it grows really fast. and will take over your tank. according to my Algae A Problem Solver Guide, by Julian Sprung, "this algae blooms under good quality water conditions, and it seems to have a positive effect on water quality, though it may shade or smother corals."
i would vote to take it our if you want corals. mannual removal is the only way known.