black algae

Question
I have had a saltwater tank set up since May and have noticed some black algae starting to spread, from the rocks to the sand. I just changed the lights. This is ugly stuff and is growing over some of the live rock.

Answer
go to about.com and click on games and hobbies. Next click on saltwater aquariums,[lower left], there you will find almost any answer you need. There are many types of algae and this site will help you identify, and then get rid of it. All the best, Gerry.