I'd observe him for 3-4 weeks. Watch for anything that seems weird like strange poo, spots, anything unusual. *IF* something shows up, then ID and figure out next step. Hopefully nothing shows up and continues to eat fine and moves from QT to DT normally.
If it makes you feel better... my QT is just 5g for my 180g ... My 5-6" yellow tang got to "vacation" in QT last month for 3 weeks - wasn't thrilled but my DT had Reef Flux for bad algae in it and yellow nearly died. Yellow survived, when the Reef Flux was over and after charcoal, yellow tang got to move home. ... but so my sailfin tang did not treat the yellow as "new" fish, it went to sump for several weeks, then used an acclimation box to move my larger sailfin up from sump into DT ... it took patience. QT is not ideal, but its just for a little while...