That's interesting. I have never had it on the front glass but always on the back and some on the sidesA reef tank without coralline is like a forest without moss: not seasoned yet! I let it take over the back and non-viewing side of my tank, love the look personally. Sure it takes some diligence to keep it off the front, but it outcompetes much uglier and more annoying algaes. Moar! Wish I could get more red to grow though, mostly purple with some pink here.