The valve appears to be a flat cap, there is no injector on the top, just a block off plate. Filox is a backwash media. I believe the original media was birm, just backwash also. The air injector was to help the media attrack the iron. Some water treatment sights mention air/oxygen injection to help the media perform better. Just wondered if leaving the air charger in line is a good idea.

I will also look for a 1.5 cu ft tank.