Thanks for your replies
I think i'll go for a paintball bottle, it's cheaper, but it's also harder to find a regulator.
The paintball store offered to change the pin-valve of the bottle for a ON-OFF valve. This doesn't have a pin and can be turned on-off at will. Can i connect a standard regulator to this on-off valve? Or is the Hydor rechargeable system compatible with a paintball bottle?
How do you hook it up?