I just thought about something that will cause this to not work with the aquariums as they are now:
The way that the aquariums are put together will result in a small space between them on the bottom when the two matching end panels are removed. The bottom panel of an aquarium is 2x (with x being the thickness of the glass) shorter lengthwise than the overall length of the front and back panels while the side panels are x taller than the height of the front and back panels. The front and back panels are x shorter height-wise than the side panels. I mean, think about it, the sides of an aquarium interlock in a special way with the front and back panels on top of the bottom panel with the side panels being at the ends of the bottom panel and in between the front and back panels, so a gap that's 2x between the two bottom panels is to be expected.
For example, we'll say that you have a standard 55 gallon (48" x 13" x 20") that's made of 0.25" glass. The front and back panels will be 48" x 19.75", the side panels will be 12.5" x 20.25", and the bottom panel will be 47.5" x 13". If you were to take two 55 gallons and remove the side panels to attach them together then you would be left with a gap that's 13" x 0.5" in between the two bottom panels.
I just figured that I would point that out so that you guys can get a piece of glass or acrylic cut to put in said gap.