Wetmorella species and Pseudocheilinops ataenia eat pests and don't bury. But they are cryptic and a few would be needed to control pests in a 180g.
Pseudocheilinus wrasses, such as sixlines, fourlines, and mystery wrasses eat pests and don't need a sandbed. But they get aggressive as they mature.
Halichoeres, leopards, Anampses, and Pseudojuloides wrasses will eat pests. However, they do need a sandbed. In most cases 1.5" sandbed will be fine.
Fairy and flasher wrasses don't need a sandbed, but they don't eat pests.