I thought this might be helpful information, so I decided to post this. I had a 24x12x12 15 gallon sitting around and decided to make it into a 12x12x24 vertical. First I washed it with a 5% bleach solution and removed the plastic black rim from the top and bottom.
I then, with some difficultly, removed the top piece of glass and added silicone to the rest of the interior corners to ensure it is water tight.
I then, with some difficultly, removed the top piece of glass and added silicone to the rest of the interior corners to ensure it is water tight.