You need to reseal the entire tank as water will eventuly work its way to the hole again. take it tio a reputable place that makes tanks. I say this because you need to get the silicone to push all the way through to the opisit side where the leak is, otherwise there will be a potentile for a week spot. with persure from the water in the tank you dan't want the front glass to clack or the sem to start leaking again. One other thing if the area that is being fixed is not completely dry the silicone will not adhear to it and will leak again.

Bill