My girlfriend's 75 gallon recently leaked right out the bottom seal of the tank. What a mess. Luckily it was made by All Glass Aquariums and the store we purchased it from gave us a new one without a problem since it was still under warranty. Hopefully yours isn't leaking from the bottom seal. As long as you can get the water level below the leak you can buy aquarium silicone from (I hate to say it) Walmart, for $5 a tube. Seal up the leak and let it sit over night. Don't use any silicone not meant for aquarium use as I've heard of some containing ammonia. And also don't forget that if you have to bring the water level to below the filter intake, you'll have to provide aeration to keep the water oxygenated. Hope I've helped.