I wouldnt think of adding a mandarin to a tank with a puffer and damsel. The dragonettes are somewhat hardy but I think a damsel might be too too much for it. My mandarin is constantly hunting, every single minute of the day. Rock in the DT wont be enough to keep a pod colony going for a mandarin.
BUT if you get an ORA mandarin you have a better shot at it eating prepared foods. My ORA one did not eat pellets or flakes or anything but pods
though, at least for the first month. Thats where the pods
and fuge came into lay. If I hadnt had the refugium set up I guarantee the mandarin would have starved in the month that it took me to get her eating prepared foods. They can decimate an entire pod colony in days, they do nothing but hunt and eat all day/