Help Fixing a cracked tank

[smokinreefer]

So I've got a standard 36" 50gallon
It was gonna be used for a sump
the back pane cracked
The crack runs horizontal in the middle of the back pane
The crack goes almost end to end
The cracked pane also has 2 holes drilled in it

Is it possible to just get a new back piece cut,
and just silicone it in, Ontop of the cracked pane, on the inside?

Or does the cracked pane have to be removed, then replaced?