adhesive for glass in an established tank?

[WhistlingBadger]

I need to add a piece of glass to my Sumatra tank to replace a cross-brace that came loose. Super glue seems not to be doing the job (one bit of glass has to adhere to a rough surface, which cyanoacrylate does not excel at) , and of course I can't use silicone or epoxy because they are toxic until cured. Any other alternatives?

 

[Colin_T]

If it's a cross member on the top of the tank, reduce the water level, dry the glass and silicon it. Let it dry for a week then top the tank up.

About the only thing that sticks to glass is silicon, which is why aquariums are made with it. Other types of glue can't adhere to the smooth surface.