Ahh, Now you can work out the 'Fish' from the 'Cop' in me
Fish are such a personal thing and you have to work out what part of the world you want to re-create. The thing I've found is that it's very hard to create an environment that suits all. You'll find Cichlids from Africa require virtually the opposite conditions to the South American Cichlids. You need to find the right fish for your personality and lifestyle. (I keep marines now)
Unfortunately we in Australia are suffering the consequences of releasing non-native fish. Please never flush or release what you don't want!