The Blue Green Reef Chromis is desirable not only for its beauty, but also for its peaceful demeanor (despite its designation as a true damselfish) and ability to be kept with almost all other community fish, invertebrates, and corals.
With this said it is supposed to be in a tank size of 30 gallons or more but...
I'm sure you could get away with a couple. Pretty hardy too bro.
Hope that helps