What size tank, inhabitants, etc?
If this is a smaller tank, less than 100g, I would just buy a new tank personally.
If it is a larger tank, even then, you need to seriously think about what has happened. If it is a bottom seal that is gone...ouch.
I would get some large tupperware containers - the 15-18g one's at least, and move the inhabitants in there with filtration etc. Even once you repair the silicon, you can't immediately refill it.