Make sure you setup your refugium sump correctly, else, it will become a time bomb and crash your tank eventually!
Damsel is pretty hardy fish so shdn't be a problem. But if u wanna introduce other fishes, then they may be bullied by the damsel. Previously, my damsel is so aggressive and it start to nib on my soft coral! Manage to get it out and leave it in my sump!
Juz my 0.02 cents!