Cracked crossbrace

[-=James=-]

Hopefully this is the right section. Doesnt seem to be a general section for threads...

I have a 180 gallon tank (72x24x24) and had a 72" metal halide fixture (3x150W) temporarily sitting on top of the tank while I was working on some things.

I have 2 large cross braces aross the tank (12" wide by 24" long) and one of the 150W bulbs was sitting directly above the crossbrace with 1-2" to spare. The light sat there for < 1 hour and I suddenly hear a *CRACK*. I hoped it was my pistol shrimp but it was too loud to be him. I find that one of the cross braces got so hot and cracked the whole width of the brace. I never thought about the glass getting THAT hot that it would crack 5/8" glass .

Is there a way to repair this? Is it safe to have a cracked crossbrace?
I know many people dont run cross braces at all and have tanks bigger than my 180. Im just concerned for the structure of the tank. I was thinking about glueing a piece of glass on each side or getting someone to fill the cracks with glue like they wound a windshield? Please provide any comments regarding my available options.

Thanks in advance