So here's the lowdown on bristle worms. As a general rule, they are harmless, or even beneficial. The "bad" ones are extremely rare in the hobby. As Mpfaff mentioned, cutting back on feeding will reduce their numbers, as they are detritivores and scavengers.
However, they can do something that crabs and shrimp do all the time. Annoy corals. Bristle worms inside a zoa colony could, theoretically, irritate the polyps often enough to cause damage. You just removed those from the colony, so IF that was the case, problem solved!
In general though, bristle worms are good to have.
Someone stop me! Please! But... not just yet...
55 Gal Tropical FW
55 Gal Mixed Reef