Step 1: Draw a plan of the aquaria with dimensions for the glazier to follow.
I've enclosed drawings that you can either have a glazier construct or cut and you assemble.
Step 2: Setting-up the finished aquariums.
The valve assembly on the top is a garden-hose adaptor with a refrigeration schreider valve screwed into it.It is also possible to feed a semi-rigid plastic tube to the top of the upper aquarium and vacuum through this. When the water reaches the top, shut-off the vacuum-pump and remove the tube. The water will remain in the upper tank as lon as the lower tan level covers the entrance to the upper tank.
Step 3: Schrieder-valve + garden hose connector details.
Also shows "leak-testing" the upper aquarium.If there is a leak, air comes in [note the air bubbles in the corner] this can be marked, water emptied, dried and re-sealed.