Fun addition to your sump, which is where these grow and multiply for me. Most people who started their reefs with live rock are familiar with the smaller white hard-tube worms; these have fans about the size of a pea with nice color. Closely related to Christmas Tree Worms, except they require no special care and reproduce in captivity. They don't like light, so they won't get out of hand in your display. 5 worms, either loose or attached to a small piece of rubble from my sump. Just toss them in a low-flow area of yours and you're good to go.