Sorry if i missed this in the text, but why are you resealing it? Does it leak?
Do a fill-test out on the balcony, and if it doesn't leak don't worry about it. Without direct sunlight, rats or nibbling loaches the silicone should last, well, pretty well forever.
If you're cutting silicone away you should clean it all out and re-set the glass panel. I had to do this 3 years ago as my tank is a 2nd hand ancient thing and 1/2 in the sun, and it looks like my paranoia might make me do this again this summer. Not looking forward to that, though I might re-build into the wall at about 2.5x the volume.
If there's a big crack just set a 1/4" sheet of glass over the crack and silicone (the hell out of it) into place to hold the main panel together.... unless you want it to look nice