Why not cichlids? I'm not talking KILLER cichlids, but I have brichardi, which are beautiful. They are aggressive when paired up to breed and after keeping them in my community tank for a few weeks, I would not do that again (but as my sig implies, I never wanted a breeding pair and thus got yet another tank
). There are so many types of cichlids that you could have a tank with the less aggressive ones. Look into Lake Tanganyika cichlids, which include Neolamprologus brichardi, Neolamprologus pulcher and shellies (I have Neolamprologus multifasciatus)!