I have a 75 gallon tank that sprung a leak about halfway up. Eons ago my wife got a gumball machine turned aquarium but it leaked like a sieve. I undid the silicone (plastic to plastic) and used the Waterweld to seal off the bottom. It held perfectly the whole time we had that tank. That was freshwater though and 13 gallons. JB Waterweld is supposed to cure and work underwater in as much as 1000 gallons. Has anyone used it to reseal a seam in SW? Can it bind to old silicone? Even if it only worked for a month or two it would be a huge help. With Christmas coming there won't be much left for discretionary spending for a while so I'd like to get my 75 up and running if it can be done. Thank you.