Center support on 48" tank

[earhtmother]

Have a 48x18x18 tank that has no center support/strut. I would like to put something in to support the 10x48 piece glass I use as a lid as it looks like is bowing slightly.

 

[JackBinimbul]

I'd, personally, just get one of those slim metal rulers, cut it to length and put it lengthwise under the piece of glass, on the lip of the aquarium lid as a support.