this is just my opinion but i think a clownfish would look nice but if you want something else most gobies and dartfish including firefish would work fine or a damsel fish if you keep it alone or with tougher fish
If not I would go for captive bred fish. Most captive bred fish are easily fed and easy to care for. (And it will help wild populations witch is a win win)
yeh i reccomend a clown or two because i have one in a 20 with a firefish and neon goby but there others thatd work for a 30 as well but im liking the anemone idea myself too bad i dont want to risk one gettin my other two fish tho they are special to me
A colony of barnacle blennies, a stigmatura blenny, firefish, zebra dartfish, neon goby, a watchman goby, a royal gramma, yellow assessor, orchid dottyback, swales basslet, Wetmorella wrasse, pink streak wrasse, and sunburst anthias are some of the possibilities that I would choose from if I were in your position.