It grows in tufts mostly, as opposed to a carpet. It's not hair algae. It reminds me of the fuzz on the back of a fuzzy ****on, if you've seen one. I did have a ****on, but the CUC ate the fuzz off his back the first day. Nevertheless this could be descended from it. It's not 'taking over' the tank, but there is more of it than I want to see. Ever seen it before??