I would look at recycling glass. I built a few glass tanks (mangrove pot, top off reservoir, etc) from tanks that I found on the side of the road or from Craigslist. Can save you a ton of money and a lot of tanks that break still have great glass in one piece.
i just recently had some glass cut for my sump at home depot. It was really cheap there, i just went in with my dimensions and the cut it for me. You may want to call before you go because a lot of places dont do it anymore. because my piece i needed was small i only paid like 1.50 for a square foot i believe. not sure the thickness of it though sorry!