While there is no reason to dive nitrox at those depths, divers who have their own tanks often will have nitrox in them. In our case, we topped our doubles off with air after a nitrox dive. That was enough nitrox to be problematic as far as the rules go. Had we known we needed air only, we would have drained them in advance and not lost time in the habitat because we wanted to use our own gear.
It is a hoot! You should do it. We are planning to go back.
Trace, I was looking at the photos of the lodge and the entrance photo has, what looks like a hooka (second stage regulator on a long hose) coming up into the moon pool. Was there a surface supplied hose system there when you visited?