I'd drain the tank 50% (or even all the way if you can move the fish temporarily) to take pressure off the brace. Then use a 2 part (plastic) epoxy directly on the affected area. You can even cover the glued area with silicone once it has dried if you're worried about the epoxy ever affecting the water.
This....
You may also want to add a euro brace under the frame to ensure even more stability. I've added a 4" wide 3/8" piece of glass (front to back) to a tank before with success using GE silicone I; which would be very easy to do if the tank is drained or even partially drained.
This....
You may also want to add a euro brace under the frame to ensure even more stability. I've added a 4" wide 3/8" piece of glass (front to back) to a tank before with success using GE silicone I; which would be very easy to do if the tank is drained or even partially drained.
