Without clear boundaries to defend, the fish become more tolerant of each other and since there are more fish, the aggression is diffused over more targets. Obviously, overcrowding can quickly cause the demise of your tank. So, careful planning is necessary to increase the abilities of your filtration system to meet the needs of the increased bioload. An almost absolute requirement when overcrowding is a step-up in frequency of water changes. Breeders and advanced hobbyists who use this technique can be found doing daily water changes, whereas the average fishkeeper can get by with weekly or biweekly changes.
Filters have to be watched carefully for clogging and cleaned out often.
Nitrates build up quickly in an overcrowded tank, and the easiest way to reduce levels is through water changes. You should discuss your tank's bioload capabilities with someone who has experience with Cichlids. In nature all is not perfect- fish do die from conflicts and disputes. But in tanks, loss of fish is both unpleasant and dangerous to the well-being of a closed aquatic system. You will never obtain a perfectly peaceful community as it is Cichlid nature to quarrel and fight for territory, as for any animal.