Enough Gas Exchange?

[Oxymoron]

I believe that airstones in a reef tank are unnecessary and not needed as long powerheads are positioned to continuously roll water from the bottom of the tank to the top. Your dual overflows and the use of a skimmer should be more than enough. Airstones can also introduce micro bubbles in the display which are unhealthy for the fish. And there's also a build up of salt creep from the spray they create. Hope this helps. Others may have other opinions as this is a topic that has been argued about many times lol.