My Argentea. It is a fairly peaceful tank though because the only cichlid other than my Argentea is a small Severum. I can't put in other cichlids or my Argentea will give them hell.
In my 125 it is my male Trimac, especially at feeding time, he chases the Red devils the most. In my 75, it was my Black Nasty until very recently, now my Oscar has decided to stop backing down and has taken over as King of the 75. My Oscar may end up in the 125 if he picks on my Hait. to much.
all my tanks are pretty calm... so far... my (4.5") indo and (6") chinese algae eater are trying to figure out who gets the small space under the pile of driftwood... for now i think its a draw...