Have mentioned this in a previous post I think. I use 'Youngs Steriliser And Cleaner' in my ultrasonic. It is also a deodoriser so removes any residual tastes in the cartos. I use it as a steriliser for home brewing, its available at 'Wilkinsons' and home brewing suppliers. Milton is a great steriliser, but can be corrosive on certain metals, especially brass.