I'm guessing from the "FW" comment, that you read the other thread about the
red flatworms. Don't panic - panicking only makes things worse.
If it is the red flatworms you're worried you have, just take a deep breath and
start reading the archives. FW is a freshwater dip. They fall off in seconds. This is good for the person who has just accidentally infected their tank by introducing a rock with some on it. (That's why I jumped in the other thread about taking care of it right away.)
If they're everywhere, still take a deep breath. They aren't going to nuke your tank overnight. Do some reading, and let us know what you're thinking, what you're worried about, and we'll see how we can help.
Now, if I'm wrong, and it's some other worm you're worried about, you'll have to be more specific... there are billions of worms that can show up in reef tanks. Most of them are fine. Some of them are a PITA. Few of them are really dangerous.
Danielle
PS. Ironically enough, the flatworms are photosynthetic to a degree - turning off the lights and darkening the tank will also kill them. Unfortunately, it will also kill corals, so that usually isn't an option.