If they are small and white little dots running around then they are Copepods, they are a good thing and every tank has them. They are eaten by some fishes like Mandarins and Dragonets. They will not take over your tank as they usually take to the rocks during daylight hours.
If, however, they are hard spiral type things on your glass then they are Spirobid Worms, again most tanks have them and they arent harmful. If you must get rid of them you can take a plastic scraper/razorblade and take them off.