Any of these (preferably less than 3-4): Royal Gramma, blackcap basslet, fridmani basslet, flame hawk, six line wrasse, percula/ocellaris clowns, starcki damsel, long nose hawk, bangai cardinal(s), watchman gobies, bicolor blenny, chalk bass, flasher wrasses, lubbocks wrasse. All are pretty mellow, stay small, and are very hardy.