I had this stuff come around when I lowered my lights. I took this picture right before I took this piece out and scrubbed the nastiness off. I didn't put it back in the DT, I threw it into the fuge and it's been free of this brown algae since. I don't have my params... "boo!! hiss!! " I know I'm heavy handed at feeding. Once I saw this, I slowed way back on feeding and fired up my GFO reactor and up'd my water changes. It's mostly gone now, but some of it still lingers around. I have just never seen this before. It seemed to start from this one piece of rock I have had on the right side of my tank. Well, I decided to glue an acan on there and move to the left side of the tank. I was interested in what would happen with the acan mounted like this, I didn't think this would happen though! Haha! But, I do have a picture... If that helps. Thanks!