Yes, cichlid fish are aggressive. Despite being advertised as community fish by most pet stores, cichlids are very aggressive and territorial. They’re known to fight among themselves and attack their tankmates.
You can minimize their aggression by:
- Providing them with ample space in the tank, especially horizontal space
- Avoid overcrowding the tank
- Housing them with fish that have similar size and temperaments
- Feeding them appropriately
- Providing adequate covers and hiding spaces
- Periodically rearranging the tank to break territorial strongholds