Is it long and hairy, fuzzy or just look like pepper sprinkled on the substrate/rocks?
The general cure for most algae problems and copying myself from another thread:
Algae should be reasonably easy to control. Skim heavy, use good macro algae, check your RO/DI, check the lighting (bulbs) for over-usage, cut the lighting cycle, ease up on the nutrients (feeding), bring in the right kind of algae eaters then possibly add GFO, Purigen and/or a UV Sterilizer. Once you get the changes in, do a sweep on the algae getting as much out of the tank as you can. The rest should take care of itself.
