i would not use a razor blade do to etching your glass. There is a blade they make but it is not really sharp. It removes it quickly and effectivly. As with any algea or plant in your aquaria, it is beneficial as it will keep calcium in moderate levels and absorb other nutrients that harmful algea needs to survive. But as i'm sure you have realized by now, almost anything in excess in the reef tank is never a good thing. Moderation is key. I personaly leave a little on the back and overflows for this reason. Just don't let it cover completely. An urchin is also a natural very effective way to do this, but they also have their down falls, they will pickup frags and other items to disguise themselves.