Thanks everyone! The system itself is really nothing new. The inspiration came from threads by some guys on this forum, like Bill Harada and Steve Colley. I originally built the system to be displayed on the wall above the tank, which is why the equipment is so overboard, but a lot of it is absolutley unnecessary overkill!
kzr750r1 - the actual calibration took place with an ouput hose from the pump feeding through the check valve, and directly into the tank - exactly as a normal dosing would take place. The picture is just to show the pipette used. Sorry for the confusion!