i bought 3 chromis for my first tank and they all died off 1 by 1. could it have been a disease specific to chromis? maybe. all my other fish are thriving so far.
i was recently recommended by my LFS to get the firefish in groups... i bought just 1 for now but i can see how it would be nice to have them in a group of 3 or more.
They're also prone to catching Uronema marinum, and I've had other hobbyists show me "wounds" on deceased fish they suspected was from their Chromis attacking each other that were actually from the parasite, Uronema is pretty nasty.