Dana,
First of all thanks for replying to my forum. The sherwood Brut is fantastic for nitrox, and can do up to 40 percent with out service, ( depending on how old they are) but cxan be servoiced to do nitrox. As far as tanks go once you have tanks cleaned for nitrox, you SHOULD use only nitrox in them. If you know your LDS has a good air system, sometimes you can use regular air. I have a clean side to my system so I can fill my nitrox tanks with air.