I am newer to Oscars and Vieja, but I am not new to cichlids in general, or sunfish. I have been keeping sunfish for ten years, only taking a break when I was in college. I kept several sunfish (with convicts) for about five years in water that was mid 70s, until I gave them to my Dad for his classroom aquarium. I currently keep six species of sunfish, including an adult bluegill with sexually mature Synspilum and Severum. That specific group has been together about 6 months. The sunfish I was referring to that I said was too aggressive for tankmates was a Green Sunfish, that was especially aggressive (and an aggressive species) and he would not allow any other sunfish in the 55g tank. He did allow catfish and plecos. So yes, I have kept adult sunfish with adult cichlids, and yes I have kept sunfish for a long time. I have noticed no difference in disease resistance, vitality, aggression, or color, based on whether they are kept in low tropical temps, or without a heater. You may want to actually know me and my experience level before discrediting everything I say.