I have a school of 17 chromis viridis, lost 4 in the beginning.
As they are cheap and abundant there often not properly cared for in the trade.
Forgot to mention I used to have a 75 g tank and of the 7 only 3 remained, so it could be hit and miss.
But for your 180 g I think you could try.
Make sure not to fill the tank with coral and live rock but leave enough space ABOVE the decoration, so they can behave as the do in nature. (more or less...)
I was to the understanding that the chromis attacked each other more than die of unkown causes, is this not true??