Fish like Goby paired with a pair of pistol shrimp perhaps. Royal Gramma will sustain too. Pygmy wrasse or a blenny might work as well. Royal grammas do tend to claim a region of the rocks as their personal territory. But if you add them to an established tank, they have problems finding their personal grounds and might get stressed.
Peppermint shrimps are a bit notorious, some reef tanks and clownies do just fine with them while others just can’t adjust.
Other candidates can be cleaner shrimp, hermit crabs, urchins, and snails – they are peaceful and will act as your personal clean-up crew. Moreover, they do not take up too much bioload.
All cleaner shrimps are amazing additions for the tank since they keep the habitat clean or try to and they are pretty stationery and don’t move around too much.