Well, you could
tho the cleaning job will be a pain in the neck... Obviously this tank isn't that clean...
The sealant in between the glass is for structural strength, the watertight seal will be the silicone bead in the corners. The issue is, silicone sealant hates dirt and grease, thus the glass surface needs to be spot on clean. If it isn't you will see an air bubble form under the silicone. Then you know it wasn't clean...
Thus, it's something you can't often see upfront, it might look clean, and it needs silicone to show you it actually was not.
Then it's too late... A bummer...
You need to cut all old silicone out of the corners and scratch any tiny bit from the glass, in some cases long term calcium staining can etch into glass and give it a slight stained milky wash that you can not get off, no matter how long you rub it. Also in scratches in the glass dirt can build up that is impossible to get out or to inspect for cleanness, after all, it shows as a white coloured scratch.
Anyway, after cleaning all old silicone perfectly out, degreasing with acetone is key... A finger print can be enough for silicone not to bond. Thus gloves are key as well.
So it's always trial and error... And being a tad lucky, if you like a gamble and do all the work, then Rock & Roll and hope for the best and it will stay good in the long run.