If the silicone is very thick where you are applying it, I would wait a minimum of 3 or 4 days. I would wait even longer if the weather is cold or humid. Curing the silicone is very important. Are you sure that's the only place it is leaking from?
If all else fails, good places to look for bargain tanks are at garage sales and local classified ad papers. Sometimes eBay or Aquabid.com will have a tank in your area for sale. It doesn't usually make sense to have one sent, but a pick-up would work fine.
Welcome to the tank
