if it is diatoms it will eventually run its course with water changes and time.so long as you dont overfeed leave your lights on all the time etc.
its quite ugly to see so you can use a turkey baster to suck some up or blow of rocks and a mag for the glass
some people say disturbing it makes it worse some say distyrbing it does no harm at all
ive done both lol
better to get a proper id on it first though so you know what your dealing with