Sweetlips get rather large,30 inches,So it would out grow your tank quick.
A Dwarf Angel would do good in a 30g
I have a Coral Beauty,Colorful and very active fish. I originally wanted a Golden Angel but after i bought the CB they got one in,go figure
A small list of fish that are great:
-Clownfish,So many to choose from.
-About any Goby
-6 line wrasse
-Blennies
-Royal Dottyback
-Psuedochromis (Not too sure about all of em)
-Cardinal Fish
Good luck!