One thing I forget to tell about the tube, is how its kept in place now that the early scaffolding has gone. It's a balloon trick!
You see, there's a wee balloon on the inside that gets inflated, if you can inflate something with water, so that it acts like an anchor on the inside. Sort of like a harpoon, Dad? asked Keir - well yes, but with smoother edges. On the outside I have a 'bumper' that I need to keep close to the surface -except for the daily twist and clean routine - and that way I've a tube retaining mechanism.
It seems though that the water inside gradually evaporates, gets out or generally reduces in volume - they didn't seem clear on how - so I get to use another valve to extract last week's remains and top up with a new 5ml syringe. Sciencetastic.