You must be Nitrox certified. We use a membrane system onboard so our Nitrox percentage will be between 31-33%. You can use our tanks or bring your own. If you bring a O2 clean tank “YES” we can fill it but it will no longer be a O2 clean tank because we use a membrane system. When you sign up for Nitrox, there is a set price for the trip (posted online and on the boat) that includes fills for all your dives as well as a full tank when you leave the boat. If you bring your own tank, we will fill it before the first dive if you need and it will be filled before you disembark.