When I was watching my glass guy making tanks, a small bead of silicone was placed on the edge of the glass, a second pane was pressed into the silicone then the excess was pressed onto the joint to create a thicker bead along the length of the joint. If you did not separate the glass panes when you did the reseal, it may be that the reason the tank leaked was because there was not enough sealant present to keep the glass from shifting from the water pressure. Since silicon stretches, it needs to be thick enough to not stretch so much that it releases from the glass. You obviously have enough silicone present to cover whatever leak there was but can't say that it's enough to stop a new leak from happening over time. You can actually see how this works by pressing a piece of chewed chewing gum onto a piece of glass then try slowly pulling it off. You'll see the gum stretch ( as will the silicone) then smaller sections will lift off the glass then the rest will either lift off or pull apart into separate pieces. That is what happens to the silicone on fish tanks that are improperly sealed. :^0 
