Powder blue and powder brown tang.

[gbrewer1]

Have a 150 gallon and wast told if put together at same time may work. Opinions? I have a yellow tang and a sailfin in there already.

 

[bang guy]

One of them will attempt to be dominant and the loser won't thrive. That's just based on tanks I've seen with both, I have no direct experience keeping them so you may be fine.
From my perspective it made the tank tense and not relaxing at all to view.

 

[gbrewer1]

I tried it before and they did not bother each other but, I have a salfin that went after both of them and they did not make it.

 

[btldreef]

I wouldn't risk it, not in that size tank. a 150 isn't all that big, especially when talking about Acanthurus sp tangs. They can be quite aggressive. A 150, in my opinion, is barely large enough for a full size adult Powder, let alone two.