I use them on my 200 lit tank till my tunze pressurize arrives I use tetra diffuser on top so any gas escaping goes in the tetra diffuser and it is not lost never tried to refill them.
just reliesed these dont come with a night shut of valve is it easy to fit a cheap on? as the next package is about an extra £0/60 which come with a valve!
Yes as long as it is German standard but you have to know that the needle valve for adjusting the bubbles is not one of the best it is somewhat sensitive to adjust.