I can't quite recall the brand as its been a while but you can try getting silicone that dries immediately under water. It is used for boats, ponds and swimming pools and it is actually aquarium safe. I've used it in the past to temporary hold a tank. It's especially useful if you get a piece of glass to stick on top of the leaking area. It is also very strong so it will hold on its own as well.The leak has slowed by about 1/2, , and since the tank is outside on the patio, the water won't cause any damage.
I actually just spent some time reading about it. Scary stuff and if the predictions are anywhere close, it will be a tough task to escape it as there'll be no warning. It will be a devastating event...which is actually overdue according to calculations..We live in the Cascadia Subduction Zone. When the next big one goes off, I don't expect my house or fish tank to survive. We'll be lucky to survive with our lives. If I happen to be in our little town when Cascadia goes off, I will need to get to higher ground before the tsunami wipes out the town.
https://www.newyorker.com/magazine/2015/07/20/the-really-big-one