LF glass brace for 90gal tank.

[hillegom]

As JL said, get a piece of glass cut, the width, length of your broken centre piece.
Use silicone glue to marry the two pieces.

I just bought some glue (not a glue if you believe the propaganda) from can tire.
I have not used it yet, so can't give a review. But it is what I would use in your case. Repair the crack with this glue, then repair it again using jL'S suggestion.
http://notaglue.com

If you need help, pm me