I grow out different species together, but try to never put similar body and mouth types together, or those with similar color patterns. Especially if dealing with territorial, predatory fish such as Parachromis and Caquetaia
Not so much because I couldn't tell them apart, but because they will see each other as competitors and kill each other.
I find similar appearing young cichlids to be extremely hard on each, and as stated above, those with faster growth rates will kill any even slightly smaller individuals. And even if they don't physically kill each other, the larger individuals intimidate the smaller into stress induced disease.
Those I put together successfully are usually those with very different body types, and not usually oredators.

