You will not only have to empty the tank to reseal it, you also need to give it 48 hours of dry time minimum before you reassemble it. If you do it sooner, you can lose your aquarium livestock due to chemical leaching, regardless of the type of silicone you use. Additionally, if it is in fact leaking around the seals, and not the result of a crack or fracture, you will need to remove the old silicone in order to reseal, as simply placing new silicone over the old typically does not fix the problem. Good luck.
"Listen to some of these guys talk, and it's like they were born from their momma's belly with a fishkeeping encyclopedia in one hand and an API kit in the other" (unrevealed).