I started out with 3 chromis. 2 of them disappeared for no reason it seemed. The 3rd started to get shy so I decided to get a clown. They have been "buddies" since and now the chromis is very brave. 2 or 3 is good to get as they are schooling fish. I've never heard that they kill each other. They are peaceful schooling fish, but are considered in the damsel family. Damsels are aggressive and can bully each other, but not chromis.
“Success is walking from failure to failure with no loss of enthusiasm.”
- Winston Churchill