I had a big chip in the front corner of my last tank (97g) and you could actually see into the tank through the gouge. We stripped all the inner seams, installed an inner cleat along the front bottom and redid all the seams. I'm sure the same could work for you.

I would just go to glass shop and get a peice of SALVAGE 10-12mm and replace the panel. Its a easy fix IF you know how to properly rebuild a tank, other wise it will just cause more issues with leaks and other stuff
OR
If that panel is against the wall and not seen you could double glaze it with another peice of glass if your afraid of rebuilding the tank. I have done that a few times on larger tanks, infact I did it on my uncles 260g turtle tank
But I would replace the side.... Just cuz I know what it feels like to come home and find a tank flooding your place

I really appreciate all the advice guys. I think I'm going to fix it one way or the other by having it filled or just replacing that pane of glass. Not sure how much that'll set me back but it's more than likely worth it, as long as I don't tell my wife how much I spent :mrgreen:

Get salvage glass if you arnt to bothered by scratchs or other imperfections that make it unsuitable for things like shelves and table tops. I usually sell it for 1/2 price

Where do you get salvage glass? Is that what it's called if I call around? I'm not worried about looks since I'll probably paint it black or add a black backing.

Call around to glass shops and just ask if they have any scrap, scratched up 10 or 12 mm glass. Most larger operations do or even call a place that makes aquariums they might be able to cut you one for cheaper then a glass shop