If your tank is really leaking, and it's not under a warranty, I would probably advise you to bite the bullet and get a new tank. The reason is that you probably have more invested in livestock than the tank itself, and getting it fixed means that your livestock will be in tubs and buckets for several days at least, and you're probably going to lose some of it. Once you've transferred eveything to the new tank, you can get the old one fixed leisurely and sell it to recoup some of the cost of the new one.

Think of it as an opportunity to upgrade!