What are the dimensions of the tank? 30 gallon is too small for most mbuna, peacocks, and haps, but there might be a few dwarf species you could get away with. A colony of Pseudotropheus Saulosi would probably work - 1 male with 5-6 females.
Have a look at the cookie cutter section for 29gallon.
When you find something you like, post here for some advice. You can't just put anything in a 30 gallon unfortunately, I recommend some reading and research before buying fish.