I'd recommend you make or buy a nice heavy wood canopy, paint it or stain it to your taste. Then the fish can never actually jump out. Very easy to get a design to use by looking at tank set ups for sale in shops, then make your own; or buy one ready made.
I have large zip lock sand bags on top of my glass top. It works well as the sand will absorb the hit and does not break the glass like a rock would. Learned from glen and knock on wood this is the first arrow I have not lost due to this reason
This works great!
My wife made me black canvas bags filled with sand about 6x4" - dozens of them. They work really good and do absorb impacts which will prevent the glass from breaking.