Scuba Tank Sizes

[lottie]

Okay, I'm showing my dive naivety here.

What is the difference between the different sized tanks out there? - I'm just talking about the recreational tanks (not nitrox). Also is there a difference between Aluminium and Steel? (apart from the buoyancy aspect)

So for example: if a diver (okay, me) was at a steady 60fsw, not hoovering up my air with the tank filled to 3000psi. Would the different tank sizes make any difference to the length of time that i was under the water?

I just got back from doing a dive and took a smaller tank (normally used by the DMs/Instructors) rather than the normal (think they are AL80s - whatever that means) - so i was only under for 31 minutes instead of my average of 45 mins

Thanks