,thanks for your reply Sharn. I'm just trying a new method. I have an old Fluval which I have taken the filter chamber off. Replaced it with a large piece of rubber hose which has a protective gauze attached to the end(so fish don't get sucked up), then I have fed the co2 tube into the rubber hose, that way the bubble gets sucked into the rubber hose, then the filter head, goes through the impeller, chomp chomp and is spat out the oulet in its new thousand bubble shape. Do you think this would be ok? :roll: