I like the question. I’ve got a small watchman and pistol in a 29 gal sps tank. This MAY be of some small use- My shrimp and goby aren’t completely paired. By that I mean the shrimp has made a labyrinth throughout the entire tank and the goby has a designated, specific home at one of the many tunnel entrances; he’s always there. I have a starry blenny, urchin, and typical CUC... everyone is cool with each other. I very seldom hear the pistol shots anymore. I hand feel him a chunk of fish every few days as a treat on top of whatever he’s scavenging. Everyone is satisfied. In MY tank, I’d like to and feel comfortable adding a mate to the GOBY ONLY. I’d feel 100% okay doing that. Adding a 2nd shrimp... that second shrimp could quite possibly even kill the original shrimp.