Can you add a board the size of the tank (if you have to paint /blend in) to help more evenly distribute the weight. Hanging over that much may very well cause enough sag to loosen caulking in seams, imho
I have one - the trim is ~1/4 inch each end and front and back and the glass sits inside the trim. If it was off the table at the ends I wouldn't worry as much, but the long sides/ front and back - are probably the more weak point.
If you do it make sure to keep it level.