Is it normal for a powder blue tang to twitch ?

A friend has got a 120 gallon saltwater tank he has just purchased the little kritter he has put it in his tank a few hours ago acclimitised etc and the tang keeps twitching.Their is no visible signs of stress or disease and he aint been bullied he looks really settled just minus the twitching ??? his setup is a FOWLR,external filter,heater,ozone,protein skimmer,wavemaker, hes a got a couple of nemo's, royal grammar, 2 chalk gobys,a few chromis,cleaning crew etc nitrates 10 ph 8.4 amonia 0 phosphate 0 salinity 1.024 temp 78 phosphate 0.