I had a small yellow tang in a 29 gallon running a UV
sterilizer and he was fine. No problems with ich. Oh and no QT tank either. BUT, I will say this:
I concede and apologize to the Tang Police. After seeing how beautiful this fish is swimming in the new 75 gallon that he's housed in, I understand that it was a mistake to take him on in the 29. He was small when I purchased him but these guys are pigs and grow very quickly.
But anyway, good luck with your yellow tang. It is a great SW
fish and should do outstanding in your 55. Stock up on seaweed...