There are 2 different rainbow cichlids:
The Rainbow Cichlid (Herotilapia multispinosa) IS a peacefull cichlid (but can sometimes be territorial) getting to around 6"
then theres
Kribensis (aka Rainbow Cichlid) (Pelvicachromis pulcher) is well known to be more aggressive, especially when breeding, these fish get to around 3-4"
The Rainbow Cichlid (Herotilapia multispinosa) IS a peacefull cichlid (but can sometimes be territorial) getting to around 6"
then theres
Kribensis (aka Rainbow Cichlid) (Pelvicachromis pulcher) is well known to be more aggressive, especially when breeding, these fish get to around 3-4"