Yep, people are going to say that 65 gallons is too small for a yellow tang but opinions vary. I feel that 55 gallons is where you move into a "gray area" meaning that anything less than that I would come out strongly against while 75 and up I'd absolutely be comfy with and anything in between...eeeeehhhhh maybe...
They do seem to be the hardiest of the tangs but still somewhat more prone to problems than other types of fish. I've had one for quite awhile now without a single problem though. I'd say they're good fish, personally.
And I agree, don't count on him taking care of your algae problem at all! I bought mine for the same reason and he's been a complete BOOGERHEAD about it!! He won't eat the algae we want him to eat, oooohhh no, not his majesty Mr. Uno! He'll wait till we scrub off the rocks then pick at the GOOD algae we want to keep!!!!!
He also absolutely ADORES the dried algae sheets we put in for him. He'll rip that clip off the wall and drag it around the tank trying to keep it away from anyone else who wants to eat it