Keep in mind that you must remove all traces of the old silicone from the interior surfaces before re-sealing. New silicone will not adhere to old silicone; that glass has to be spotless.
And, of course, be careful when you scrape off the interior silicone not to slip the blade in between the glass panels. This would damage the silicone that glues the structure of the tank together. That would be a bad thing.