Looks like an "outside" chip flaring in...
If you (or a glass company) peels the silicone from the inside of the corner and re-silicones a 3/8" X 2" 'strip of glass, top to bottom, adjacent to the corner seam...that should be sufficient to reinforce the area...
I would be OK with that repair (turn the tank so that corner is in the back) But it is "Your tank, your house, your choice"...
On second thought, the tank is "junk" You should get rid of it...Send me your address and I'll pay shipping to send it to me...