Early on in the saltwater hobby, I found tons of bristleworms in my tank. I really didn't like them, as they came squirming out of the rockwork and substrate at every feeding. So I bought a Longnose Hawkfish - Oxycirrhites typus - to take care of the problem. And this fish did just that, he got every one in sight. However, it didn't decimate the population, because there are always more deep in the crevices of the rockwork. I just don't have to see them, unless I look late at night with a flash light. This fish likes to park in odd spots, like it is On Duty. :) Reef-safe.
Caveat: It may eat Peppermint shrimp, and mine was unable to tolerate Copperband Butterfly fish. Go figure.