Twice I've added groups of 7 chromis and have ended with a single fish. I don't know it they killed each other off, starved or what but mine didn't have any signs of disease.
Last September 25th I bought 10 chromis from a lfs where they had been for almost 90 days. They had no signs of euronema but I ran them through observation for over 30 days while training them to eat food coming out of a plank feeder tube. October 5th I added all 10 to the display where they immediately took to the rocks for several days. 2 never came out I now have 8. They are in with large tangs and stay together as a group. I'm feeding a lot. Almost all food gets put onto the plank feed tube where its dumped in front of a powerhead and blows all over the tank.
Speculation on my part but after watching the chromis in observation I have a hunch many may starve. These fish never stop moving. Even when hiding they still twitch and jerk like little spastics. That makes me think they are burning a lot of energy and I don't think feeding once or twice a day is going to provide the nutrition that they need.
Who knows, maybe a year from now I'll be back to one but I'm hoping the extra feedings will help them survive longer. My tank also has enough rock that every fish in the tank has their own safe place. With the popularity of NSA scapes this step is missing from many tanks and I think it leads to stress and eventually can lead to death of many fish we keep.
I failed with a group of anthia once as well. As colorful as they are I'm not willing to spend the money to try them again. I can get chromis for $8 each if I buy 5 or more otherwise I may not have tried them a 3rd time.
