Asked whether Nitrox is worth it here, Jenny Green's answer is direct: "Yes, we highly recommend diving with Nitrox."
The reasons are practical. Nitrox extends bottom time, which matters when you want to stay with the wildlife rather than turn away from it. Across several dives a day it reduces nitrogen build-up, so your dive times don't keep shortening as the day goes on. And divers generally finish the day less fatigued than they would on air.
Certification is required — "Absolutely." Nitrox needs specialised training, and it is not something to pick up informally on the boat.
If you aren't certified yet, the Nitrox course is available onboard for $200. Nitrox itself is included free on Galaxy Diver II, and costs $150 per week on the other boats.
Source: this post is drawn from a Travel eMOcean podcast conversation recorded on 1 July 2020 between Jenny Green and Jonathan R. Green.