Another thing about cichlids, is that they are long lived, and go thru many phases during and throughout maturity.
Let's take the genus Vieja, a Central American genus that prefers hard high pH water.
As juvies until about 1(even 2 ) year(s), they are very social (there is safety in numbers in nature)
At maturity, some hit it early, but normal maturity for Vieja is between 2 and 3 years.
At the time, they can get very territorial, and aggressive, so the largest tank you can afford/fit in your house,/have time to do lots of water changes on, and take care of is needed.
To me this means minimally a 6 ft tank for just a pair, preferably a space over 250 to 300 gallons, if you're considering a community.
But Vieja can be lethal if there is not enough space, or if a mate is not cooperative.
I have kept a number of them, and for at least 5 years per species,
melanura, bifasciata, breidhori, fenestrata, guttalatta, maculacauda, and zonata and their sister genus with argentea and regani.
Some have been fairly mild mannered and have done well as pairs, in 6 ft tanks
View attachment 1520277View attachment 1520278View attachment 1520279
Some I would not keep in anything under 250 gallons and might not even attempt a tank that small
Such as the two species below, and including V. maculacauda, and zonata.
View attachment 1520280View attachment 1520281
And.....if choosing tank mates for Vieja, I would choose vastly different shaped cichlids, with very different mouth configurations, because they would appear to be less than competitors for similar resources.
As adults Vieja can get very jealous of available space, and resources, and once the perceived need hits, chaos is often the result.