There are MANY red algaes and almost every discussion of red turf algae on the web confuses different types of algae. It is a dark red wine color, grows in low nitrate/phosphate environments, especially in high flow areas. You cannot scrub or pull it off --it is far to tough. It is short and velvety to the touch. It has little vine-like creepers (see last photo) that grip the rock. It can overgrow and kill some corals --I've seen it happen. The best thing to do is to control it and forget about eliminating it. It doesn't look so bad. Scroll down to see what kills this stuff and what doesn't. What gets rid of it: Put algae covered rock in a completely dark 5G bucket with heat and flow and wait about 3 months or more. It must be totally dark!! I wrapped bucket with black plastic. This worked fine and there was no trace of algae left on the rock. Yes, 3 months is a long time. Inject algae with Chem-Marin's "Stop Aptasia". I've heard Joe's Juice works also. Turn off flow and leave the stuff in there for about 25 minutes. Move slow so as not to stir it up. Afterwards, I suction most of it out with a turkey baster. In a few hours the algae will turn bright red, after a few days it will turn white, after a couple weeks you can scrape it off. I used a disk-shaped, steel wire brush that can be attached to a drill to scrape a lot of it off. If you do this, rinse the rock well with used tank water. This method will also scrape a lot of rock itself off and beneficial bacteria with it so use this method in a limited way. Recently I've noticed that some of it has begun to turn white on its own without having applied any "Stop Aptasia". Someone else said that this stuff will go thru a cycle in which it eventually just dies off. I have not seen that happen yet. Perhaps a die off may ocurr because some some trace mineral that the algae needs has been exhauasted. Good success has been reported with Short Spined (Diadema) urchins. What did not work: Tried a Blue Tuxedo urchin and he will not eat it. I put him right on the stuff many times and he can't crawl off of it fast enough. I tried a blow torch on the rock and it caused a massive cycle (in my experimental tank). Scrubbing is useless. Your brush will disintegrate before it comes off. I have not tried increasing magnesium to high levels as a method of killing algae.