In my experience, and I could be wrong, the only place you will get nitrox in 120s is with the very few ops on the island that use them: Living Underwater, Aldora and Liquid Blue. As to 100s, I can't say. I have seen that you can get them on special order from a few ops for 21% but have not seen a nitrox reference. It's probably a longshot at a very special request at best. It's a guess, but I doubt that few, if any, of these ops, sub-lease their tanks to other ops...it's really one of their unique selling points.
Not wanting to re-ignite the 80 vs 120 debate or go down the ‘my op is better than your op’ road does anyone know of the availability of hi-cap Nitrox tanks? I was thinking about dolphintam’s original post and it does pose an interesting question. To run a long sustained deep pull you may need a hi-cap tank. Which ops have access to 100 or 120 (regardless of standard / HP / AL / steel) nitrox fills? I realize Aldora has their own fill operation but they also do group dives as a standard model and I doubt they loan or rent out tanks to other DM’s (but maybe to in-house private DM’s). I started thinking about the availability of tanks for private DM’s or 1 person valet ops that catch rides on larger ops boats? To ‘rent a boat’ for a solo or a couple three divers, is not normally an option due to cost. I do not think Meridiano has nitrox 120’s available but do they rent 100’s? The desire to run long and deep means Nitrox in the normal conditions of Cozumel since the current aids an experienced diver and allows for extended diving, if running a long deep profile then the limiting factor becomes NDL with hi-cap 21% tanks.