Flat worms

[MitchM]

I've had them for years on and off, and I've never noticed them causing any harm. They stay off the corals for the most part, and the population seems to rise and fall.
I'm more interested in figuring out what they are feeding off of, and just look at them as another inhabitant of the tank.

A large die-off is said to be harmful in a small closed system, so vacuum out as many as you can before using something like flatworm exit.

Mitch