I had a school of 9 chromis, but I am now down to 8 chromis. I agree with others and think chromis are not as peaceful as advertised. If anything, the exhibit the same schooling behavior in the home aquarium as freshwater cichlids, such as angelfish and discus.
During my freshwater days, the smallest or weakest angelfish or discus fish would always get picked on until killed or removed. And once you removed one fish, a new pecking order would start all over again until you are down to just a few fish.
I feed my chromis about five to six times a day with a mixture of three different types of flake food and frozen cyclop-eeze. They are amazing schooling fish but they will fight within the group and pecking orders will be formed based on my limited experience with these fish.