If you are looking for inverts I have kept a female bird with nassarius snails,emerald crabs, and urchins. She will probably predate the snails and crabs somewhat but not overly aggressively so you will lose some over time but not the entire population. Trochus and astrea snails while not detritivores will also be fine.
I tried a brittle star which worked for a while but she got him eventually so I would not go that route.
Myles