I just posted in to answer a question on how to cut thick glass and I thought I would repost a part of that.
The best way to cut thick glass is with a water jet. Since those start at about $50,000 dollars and go up. It is not a DYI project for most. One warning is that the Jet will leave a bevel so don't just carry the glass in where a typical employee today will happily cut it wrong for you. If you are keeping both edges then you must be prepared for a gap on one side or cut one edge flat and grind the other edge flat. Diamond saw cutting will do a better job but take a lot longer and probably cost more. Of course the saw can be had for a few hundred dollars. If the glass is stressed it may almost explode in the diamond saw but then you really wouldn't want that glass in a tank either would you.
Now for me!
I am interested in recycling thick glass for charity art and stuff. Unless it is tested for strain, it can never be safely used for a tank but I am interested in glass damaged or otherwise. I am especially interested in 1/2" or thicker glass and 1/4" or thicker if it is the water white glass. If I can cut the cracks out and still end up with hand span pieces I would be interested. In some places one has to pay to take that to the disposal so I would certainly pay shipping and a bit more. In California or Nevada area, I might even pick up. I am not really looking for plexiglass BTW.