I kept my pair in a 6 ft tank alone, there were other cichlids in the tank at first, but to save the others lives, the others were removed.
As Rocksor said, they are the only endemic cichlid to their part of Cub, so although there may a number of reasons that they are the only cichlid in their natural habitat, one reason may be that way back when, they were able to outcompete, and possibly wipe out any other competitive species.
Their aggression level reminds me of grammodes, or their close cousin haitiensis.
If they can't kill other their tank mates, they may tend to die of stress themselves
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A friend of mine kept a pair in a 240 gallon with other cichlids, so the amount of space you provide will most likely be the determining factor in success or failure.