If somebody gave me a 180G right now, and my wife stopped threatening to divorce me if I set up one more tank, I'd probably stock it with turtles :lol:
Kidding aside, there are gazillions of options to stock a tank that size with cichlids. There is no way for anybody else to guess what you might like best, but here are my top 10 in no particular order:
2. Tropheus or Petrochromis
3. Lake Tanganyika community (eg. one type each of Cyps, Sandsifters, Rockdwellers, Shellies)
8. Central Americans
9. Lake Victoria
10. African River
Actually just got into turts. I have (3) 2010 diamondback terrapins 2 concentric and 1 reg. northern in a 20H, looking to upgrade to a 50-breeder soon. I told my wife if the fish don't pan out the turts can have the tank. I am leaning toward discus, itching to get something now that the tank is empty.