Actually the air was to allow the Birm to oxidize the iron. Air will also oxidize some of the iron. Birm can not work unless there is 15% dissolved oxygen in the water.
Birm can not be used if any H2S is present in the water.
I wouldn't use the air injection for Filox because it will cause ferric iron particles (rust) on top the Filox.
You will need the correct DLFC button for Filox; Birm is much lighter and will have a much smaller gpm DLFC. And less time for backwash and rinse positions.