I consider 180gal tanks good medium sized tanks for medium sized cichlids, especially if you want a community cichlid tank. (its the size tanks I have, and when I observe them I find it hard to see them being adequate for large species in a community setting
If you want larger cichlids like Parachromis, large Vieja species, or Maskaheros I consider its only large enough for a pair or trio, not a mixed community.
If you want Cichla, its really only a grow out tank.
Gourami Swami's suggestions were right on the money.
When I set up my current 180, I started with about a dozen young Andinoacara coerleopunctatus @3 at the time, but the males max out at about 7"", it also held some tetras and a pleco, and for a while some goby's.
Within a year the alpha male Andinoacara had reduced the cichlid population by more than half. Killing all other males, and a few uncooperative females.
In that size tank he seemed satisfied sharing it with 3 females.
He never bothered any non-cichlids.
I have had success in similar sized tanks with Cribroheros, Gymnogeophagus, other geophagines, and similar sized species.
The larger species often become hyperdominent in that footprint, unless kept in mated/copasetic pairs.
A northern S American community.
The tank above was peaceful, until the Acarichthys hit maturity.
Below Uruguayan community that worked well, long term
Below Madagascan community, worked until the cichlids outgrew it (about 2 years0
Below Central American non-competitive species,, but in the end the bocourti needed about 300 gals to themselves.
