I have an HFT 500 which I currently fill from a diving bottle. Do I need to also buy an adapter or can I use what I have currently? If an adapter is needed, anyone know what type?

I was also thinking of getting the more 'expensive' one as it has a moisture trap built in. Is it any better in practice than the five quid one? See: https://www.amazon.co.uk/Greensen-Pr..._t2_B08GZ88L86