I keep from six to nine in the big cichlid tanks.
What I've done with nervous fish in the past,is every time I go near I would give them just one or two pellets and take a stool and sit in front of the tank not moving much. After a while they associate you with food and don't see you as a threat. They see the danios going after the food even though its two big for the danios to eat. Works for me.