
I find in cichlid community tanks, it is best to keep cichlids with different mouth and body shapes together.
In that way there is a chance that they will not see each other as competitors.
But when colors are similar, mouth shapes similar, body types similar, that is when aggression gets intense, because they instinctually recognize, "this dude will try to eat my food", "this blue spangled dude looks like me, so I believe it wants my home, or my girl", "this dude needs to be off my turf.
This is why I never put 2 species of Parachromis together, to different species of Vieja together, nor more than 1 species of Amphilophus together etc etc.
Below even though color was similar, was a tank that worked well. Note the different mouth shapes, bocourti being primarily vegetarian, and Chuco intermedium being insectivorous.

even then, conflicts were inevitable though not serious. Soon after I moved the groups to a from a 150, to a 300 gallon
