Let me give an example.
I keep Andinoacara coerleopunctatus, a very close cousin, and similar size cichlid to your Blue Acara.
I just searched for a recommended tank size, and of course a 55 and 75 gal were considered fine, by a number of those aquarium stocking sites.
3 years ago, a local fishermen caught a dozen Andinoacara for me, with a few local tetras, goby's and pleco.
They were put in a 180 gal tank (probably considered overkill.)
Within the first year, the alpha male killed all other males and number of females, he left himself and 3 females.
This combination has gone well for the last 2 years, BTW, he never bothers non-cichlids.
If I'd used one of the recommended tanks, 1 might be left.