Think I found it "Seriola lalandi lalandi",which means it has to be a juvenile, although I'm not sure as the fish in the tank's dorsal seems to be situated much lower.
http://www.unitedfisheries.co.nz/content/yellowtail-kingfish-seriola-lalandi
Im not the sure, the fish seems much more black (and better looking IMO) no color on tail also like the YKF

maybe a different species of mullet.