You can look into the Hawkfish. Longnose, Flame, and Pigma are large, medium and small in size. I have both a Longnose and Pigmy in my 110g display tank and they ignore each other. I wish I had more baby Trochus but I assume my Hawkfish keep their population low.
The Pigmy has quite the personality. He does not bother any of the other fish in my tank but he was also added last and is one of the smallest fish. Pigmy’s sometime have a reputation for being aggressive but I have seen none of that. I tried to quarantine my first pigmy but it was either sensitive to copper or in bad shape from capture/transit. I therefore got a replacement from High Tide Aquatics which sells quarantine fish.
My Longnose sits around the rock all day chilling out. The pigmy in contrast is constantly swimming and perching on the rocks and pecking at things I cannot see.
