Maybe I want very I wasn't very clear... I have no problem actually filling it. I understand what i need to do.
What I'm wondering is how to safely add more water as it evaporates. This means you will have to somewhat often pull the tubing apart risking breaking the glass counter every time it needs more. Getting it together once seems doable but repeatedly every couple weeks makes me nervous.
Mineral oil would prevent it from evaporating but does that affect the bubble count? If it is thicker then the bubbles move through more slowly and change the way that you count them.